The map shows where we travelled in Mexico.

Places we liked very much:
Oaxaca - for being a typical Mexican city and having amazing places to visit outside of the town (e.g. Hierve el Agua, Monte Albán) and for the nice Mexican food.
Valladolid - for being a typical Mexican town and having so many Cenotes (e.g. Cenote Zaci). It's easy to travel to Chichen Itzá from Valladolid (about 40 minutes on the public bus, cost: 35 pesos).
Tulum - for the relaxed atmosphere and proximity to the sea and the nice beach. For having amazing Cenotes nearby (e.g. Cenote Cristal and Cenote Escondido).
Teotihuacan pyramids
Places we thought were nice:
Mexico City - definitely worth visiting but it's a big city
Holbox - interesting island but crammed with tourists and expensive restaurants
Cancun - the town centre is nice and it's not too busy, the beaches are very good
Chichen Itza
Place we didn't like:
Playa del Carmen - it's like Benidorm. There's nothing about Mexico in this city, just lots of shops, bars and restaurants. The beach was overcrowded.