I just landed in Toronto from my USA - Mexico trip. Here is my itinerary and some tips:

Day 1:
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Travel: Toronto to Detroit, MI by megabus (63 CAD)
Accommodation: Detroit
Recommended Dining: I tried the Coney Island hot dogs in two neighbouring restaurants: Lafayette Coney Island and American Coney Island. Although the atmosphere in American is better, the dogs are way more delicious in Lafayette (9/10) than American (6/10).
Highlighted attractions and WHSs: No WHSs. Art Deco style Guardian Building and sculptures (The Fist and The Spirit) worth a look.

Day 2:
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Travel: Detroit to Austin, TX evening flight by Spirit Airlines (39 USD)
Accommodation: Austin
Recommended Dining: @Detroit: For lunch, I tried the Slows Bar BQ in Corktown. Brisket (8/10) and Mac & Cheese (8/10) were delicious.
Highlighted attractions and WHSs: @Detroit: Ford Piquette Avenue Plant Museum (top missing site). I saw all the early models of the Ford cars and sat in a real Model T for photo. I also saw that people were touring around the factory with a real functioning Model T. I am seconding this site as a WHS candidate. I haven't visited the other Ford Museum in Greenfield Village. Another Art Deco building, Fisher, and the Old Masonic Hall worth a look. Among all the places in this itinerary, Detroit was by far the unsafest city, particularly at night.

Day 3:
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Travel: Austin to San Antonio, TX by Megabus (26 USD)
Accommodation: San Antonio
Recommended Dining: @Austin: The world famous Franklin Barbecue was closed at that time, thus I tried Terry Black's BBQ. The brisket was heavenly (9/10).
@San Antonio: Bean burger at Sam's Burger Joint in Pearl was super delicious (9/10).
Highlighted attractions and WHSs: @Austin: State Capitol is among the most beautiful capitols in USA. I enjoyed my time and learnt many in LBJ presidential library at University of Texas at Austin.
@San Antonio: WHS: San Antonio Missions - Alamo (4/5). I really like the city itself so much. I felt the vibes of different countries while walking in the streets. River walk takes you to Utrecht, and Pearl is very European, as well the old city is a mixture of Mexico, USA and Canada. (Why Canada? because you feel safe :)

Day 4:
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Travel: San Antonio to Laredo, TX + Laredo to Neuve Laredo + Neuve Laredo to Monterrey by Flixbus (38 CAD for total)
Accommodation: Monterrey
Recommended Dining: @San Antonio: 1) Schilo's pastrami reuben and mustard is to die for. (9/10) 2) Lick ice cream shop has very nice flavour options
Highlighted attractions and WHSs: San Antonio Missions - the other 4. I highly suggest using bike share between missions. There are bike racks in every mission that you can take a bike. I took a Lyft (cheaper in San Antonio than Uber) to the furthest mission and cycled back. Each ride is around 2 USD and bikes are electric assisted.

Day 5:
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Travel: Monterrey to Mexico City flight
Accommodation: Mexico City
Recommended Dining: @Monterrey: Cabrito (baby goat) is very famous in Monterrey. I tried this in El Rey del Cabrito (8/10)
Highlighted attractions and WHSs: @Monterrey: No Whs. The main attraction is Macroplaza. Faro del Comercio in that plaza was designed by Barragan. The palace and beside modern museums are nice and free of charge.

Day 6:
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Travel: NA
Accommodation: Mexico City
Recommended Dining: @Mexico City: Contramar is an amazing seafood restaurant. I tried Tostadas and Aguachile, both were delicious (9/10).
Highlighted attractions and WHSs: @CDMX: 1) UNAM: There is really not much to see inside the buildings but the exteriors are outstanding. Thus, you can go here very early morning or after 5pm if you are short of time. Don't miss the: Pabellón Rayos Cósmicos, Mural Eppens (under renovation as Aug 2023), Auditorio Alfonso Caso, Central Library, Rectoría de la UNAM, Estadio Olímpico Universitario
2) Barragan Atelier: You need to prebook a tour from their website. I did not do that but I was lucky to find a walk-in ticket. The tickets are very expensive (6000 pesos) + for photo permission (5000 pesos). They accept credit card.
3) Old City: To visit national palace, you need to go to the Moneda street and book a free tour within the same day. They are asking you to show up 20 minutes before the tour starts for security check. I went there 10 minutes before the tour starts and was refused to entry to the palace. Keep this in mind. They are very punctual in this case.
Most of the museums in the city are free on Sundays. Try to visit CDMX on a Sunday to save some money. Museo Soumaya and Jumex are always free and open until 6.30 pm / 5pm, respectively. It is best to finish the day with these two museums.
4) Rivero Kahlo Studio is relatively very easy to visit.
5) Chapultepec Castle: There was a 30-min ticket line in front of the castle but if you are a student (even international) you do not need to wait in the line and can go in immediately for free.

Day 7:
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Travel: Mexico City to Teotihuacan to Aqueduct to Tecoaque to Huejotzingo to Puebla (rental car)
Accommodation: Puebla
Recommended Dining: @Puebla: El Mural de los Poblanos: Interior design is great. I tried Chiles en nogada and cemite chalupa. Both were yummy. They have a broad mezcal collection and you can taste them before ordering.
Highlighted attractions and WHSs: 1) I visited "Teotihuacan"(5/5) from 8am to 1.30pm. This is enough time to visit all the buildings incl. museum and take photos if you have a non-stop pace. You can no longer climb the temples except the citadel. After Teotihuacan, I drove to the aqueduct.
2) Aqueduct is OK but what most attract me there is the large cacti fields. This was a unique experience for me since I have never seen them before.
3) Tecoaque is a small ancient city with a new museum. Google maps denotes it is open until 3pm, but it this is not true. You can visit there until 5pm. After 5 pm, a visit also possible since there are no fences but just cacti to mark the borders. However, beware of the dogs! I don't think this place will be inscribed as a stand alone inscription.
4) When I arrived to Huejotzingo convent, it was already 5.15 pm. But the guard was still there. He allowed me to visit for 15 minutes after I gave him some small tips.
5) Puebla nights are amazing. It is a very artistic city. I watched a street theatre in the Callejon de los Sapos. There are plenty of live music bars and finished the day by listening a Mexican duo in one of those bars.

Renting a car in CDMX: is super expensive. I paid around 140 USD for a day incl. only third person liability (TPL), no other types of insurance. The rental fee was 70USD for day but TPL is mandatory and costs another 70 USD. They don't accept your own insurances or credit card insurances etc. No other way to get the car unless you pay to Mexico a 70 USD/day TPL fee. Driving in Mexico City can be hard for people who only drove in Canada, USA or small European cities. I did not have difficulty because the driver attitudes are similar to the ones in Istanbul. I can say that the corrupted police stories in Mexico is all true according to my two separate experiences. I will not give details about them here but be prepared for such experiences. In addition, toll fees are very expensive. I paid around 40 USD to tolls to reach CDMX from Taxco.

Day 8:
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Travel: Puebla to Cuernavaca to Xochicalco to Taxco (rental car)
Accommodation: Taxco
Recommended Dining: @Taxco: Rosa Amaranto: This restaurant has an amazing view of all the city. The food was delicious. I strongly recommend.
Highlighted attractions and WHSs: @Puebla: Not the cathedral, but Capilla del Rosario has an attractive interior design. @Cuernavaca: The cathedral was OK. @Xochicalco: Amazing ancient city. You need to first go to the museum and buy ticket to enter the ancient city. Direct entry to ancient city is not possible
@Taxco: Amazing mountain town. They MUST ban the cars from the city for two reasons. 1) It ruins the experience 2) It is very difficult to drive a long car in those narrow streets, as well as it is very difficult to walk here as a pedestrian between so many cars. If they do that, the chances of inscription will be much higher. This is a thumbs up place for inscription. The main attraction here is the church.

Day 9:
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Travel: Taxco to CDMX (rental car)
Accommodation: CDMX
Recommended Dining: @CDMX: Azul Historico is a nice place for breakfast and brunch. I listened a great heavy metal cover band in Cantina "La Castellana" while drinking Modelo and mezcal.
Highlighted attractions and WHSs: I spent the day mainly in the Anthropology museum.

Day 10:
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Travel: CDMX to Cancun morning flight
Accommodation: Cancun
Recommended Dining: @Cancun: The Surfin Burrito: The best burrito I have ever had in my whole life.
Highlighted attractions and WHSs: It was my beach day. I originally planned to go diving to Underwater Museum but unfortunately I had a flu at that time.

Uber in Cancun: You cannot call a driver from airport or Hotel Zone. But you can call an Uber in anywhere in the Cancun downtown and go anywhere you like including airport or Hotel Zone. ADO bus costs 120 pesos from airport to downtown. You need to rush to ticket booth to get a ticket or buy online if such an option exist since the tickets are easily selling out. When you are in downtown, you can then Uber to your hotel. You don't need to give 50-100 USD to reach your hotel from airport by using this method.

Car rental in Cancun: Unlike the CDMX, the cars are coming with TPL and basic insurance. And, the prices are surprisingly more cheaper. (60 USD for day) No tolls in the region and the road quality is real good. And also no unnecessary police stops here. Briefly, rent a car in Cancun region but think twice to do that in CDMX.

Day 11:
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Travel: Cancun to Sian Ka'an to Tulum to Playa del Carmen to Puerto Morelos to Cancun (rental car)
Accommodation: Cancun
Recommended Dining: @Puerto Morelos: Merkadito del Mar has very yummy aguachile (recommended).
Highlighted attractions and WHSs: 1) Sian Ka'an: For parking I paid 50 pesos. I shared the boat tour with a very nice Venezuelan family from Miami. I was asked 1000 pesos for the boat tour. I bargained for 900 pesos. I enjoyed the nature here, very well preserved. Floating in the water between lagunas for 45 minutes around the mangroves was a nice experience (3.5/5). I haven't seen any animals except fish.
2) Muyil ancient city was OK.
3) Tulum ancient city: As of August 2023, there were no parking inside the protected zone. I arrived here at 3 pm, entered the protected zone by car but could not find a parking zone and turned all the way back to my starting point because it was a one-way drive. I lost 40 minutes. Then I parked outside the protected zone and walked all the way down to ancient city and get surprised. The ticket booths were closing at 3.30pm (The ancient city closure time is 5pm). Then I walked to the exit and tipped the woman there to enter the ancient city from the exit. From 3.50pm to 4.30 pm, I visited the ancient city. They are evacuating people at 4.30pm, not even at 5pm which is the closure time. However, the city itself was small and 40-45 minutes is adequate to see all the ancient temples.
4) Playa del Carmen is a lovely beach town. I am planning a future beach vacation here with the family.
5) Puerto Morales is even a smaller village with a leaning lighthouse.

Day 12:
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Travel: Cancun to Dallas to Toronto
Accommodation: Toronto
Recommended Dining: @Dallas: Ellen's: I tried their famous Chicken-fried Steak and guess what? It does not have any chicken in it :)
Highlighted attractions and WHSs: @Dallas: No WHS. Art and Museum District is nice and art museums are free of charge.

Finished 2023 with a trip to Central Mexico. I really appreciate the community perspective information for each WHS, which I certainly made use of on this trip. All our accommodations (Guanajuato, San Miguel de Allende, and Querétaro) were at airbnb's located within the inscribed boundary or in the buffer zone. From Tijuana we flew into Leon (BJX), then used efficient/comfortable bus transport in between each city. We flew out of Querétaro Intercontinental Airport (QRO) and enjoyed a long layover in CDMX before returning to Tijuana. The Cross Border Xpress allowed us to take full advantage of Tijuana's domestic flights at a far better price and frequency than SoCal Flights. This allowed us to avoid all the hassle of crossing the border by car as we left our vehicle near San Diego during the 9-day trip. I will begin writing reviews, though each WHS has been covered well. I believe there is some relevant information to add, though in some respects my trip followed a similar trajectory as Clyde's trip from 1 year ago (of which I read his reviews and others thoroughly).

Flight from Tijuana (via Cross Border Xpress)
Day 1 - Guanajuato
Day 2 - Guanajuato
Day 3 - Guanajuato
Day 4 - Guanajuato
Day 5 - San Miguel de Allende
Day 6 - San Miguel de Allende
Day 7 - Querétaro
Day 8 - Querétaro
Day 9 - CDMX

Flickr Album: Historic Town of Guanajuato and Adjacent Mines (inscribed in 1988)
Flickr Album: Protective Town of San Miguel and the Sanctuary in Atotonilico (inscribed in 2008)
Flickr Album: Historic Monuments Zone of Querétaro (inscribed in 1996)

Extension for the Camino Real de Tierra Adentro proposed for the United States

After visiting some parts of the route in the US and Mexico, I cannot help but be hopeful that this proposal becomes a reality. After reading Sinuhe's review, I also got more interested in exploring this WHS. If an Extension is realised for the US sites, I do hope additional sites in Mexico are added as well.

https://www.inah.gob.mx/boletines/proponen-ampliar-la-declaratoria-del-camino-real-de-tierra-adentro-con-sitios-patrimoniales-de-estados-unidos

So, after two years, I found myself returning to Cancun for a weekend trip. I wonder if this itinerary is going to work:

Day 1 = Flight from FLL to CUN. Then bus from CUN to Merida (arriving around 5pm).
Day 2 = Day trip to Campeche.
Day 3 = Half-day trip to Uxmal, then bus to CUN to catch a 7pm flight.

Is this too stretched? I know I am going to miss some TWHS but I don't mind. Also, has anyone tried using the controversial Tren Maya?