I have been to every country in Central America except El Salvador and I have to say that Guatemala is my favorite - lots to do and see. I studied archaeology and anthropology in college and am especially interested in Mayan archaeology and culture - the university where I work has a wonderful museum and does a lot of work in the mayan area - it is always interesting to go to a mayan site and see a plaque honoring an archaeologist from the university. We were just in Mexico in May 2009 and had the opportunity to visit many sites during the 10 days we were there - Uxmal, Edzna, Palenque and a few others - if archaeological sites are your thing - than you can not beat Guatemala and Mexico!
Denise