There was a very handy trip planner for Mexico that used to work well but seems to be having some problems right now. I'll throw in the link just in case it's a temporary outage. I haven't used it for a few years, but it was very helpful. It included tolls and everything:http://aplicaciones4.sct.gob.mx/sibuac_internet/ControllerUI?action=cmdEscogeRuta
This sites are also helpful:http://www.mexonline.com/index.htmhttp://www.mexicomike.com/
Mexico City is quite an impressive place, as are Guanajuato and San Miguel de Allende. Sayulita, on the Pacific coast, is a nice touristy beach town. Cabo Pulmo in Baja is not touristy yet, but it's probably way out of your way. Mayan ruins in the Yucatan are not to be missed.
I've always been partial to Belize, because they speak English down there.