Sergio,
I have worked a couple of years ago in Mexico, located near Coatzacoalcos, in the Gulf coast. I have visited many great places close by (say in a 500km radius...). In my mind, there are two such places that I will never forget:
1. Laguna Catemaco (between Coatza above, and Veracruz), a volcanic lagoon amidst dark volcanic peaks and luxuriant vegetation (Medicine Man movie was shot close by). Dawn there is simply magic;
2. Cascadas de Agua Azul. These waterfalls are close to Palenque, and are simply beautiful.
Mexico has much more to offer (you should check the book "Mexico, a higher vision", that displays a fantastic collection of aerial photographs), but these two places I will never forget. And the people are so friendly! Mexico city and environs are a mini-world in themselves, but of course Teotiuhacan and the Anthropology Museum are a must. And the warm facades of the Zocalo at sunset are somethinhg to remember.
Just enjoy.