What about Ecuador??
Cuenca is considered to be one of the most beautiful cities in the world, a world heritage site. Havent been there in a long time but I remember being gorgeous.
Guayaquil (my hometown) is like the SFO
of South America, that is one city that has improved tremendously over the last few decades. All the people that I know have visited tell me the same thing.
From GYE you can also take a trip thru the 'Route of the Sun', where you can visit many different beaches that a very close together.
In Mexico, get yourself to Guanajuato and San Miguel de Allende, those are two beautiful towns. My favorite beach there is Huatulco.