Advice, por favor

[MNRon]

My traveling companion and I will be in Guanajauato for a couple of weeks in August, staying at the Casa de Dona Ana in San Javier and taking Spanish classes near the center at Escuela Mexicana. I am a retired history prof, healthy, in my sixties, and like to walk and chat with locals as best as I can with my low-level Spanish. Fine dining is not a priority, just solid, simple food. I'm the kind of guy that enjoys talking with construction workers, if you get my drift. We will hit a few museums and are hoping for a day trip to Teotihuacan.

I spent a month in Argentina last summer and managed to survive :) for a month, meeting only one other US citizen. I think I have to taxi from the airport figured out, and done enough on Google Earth to know my around town, I think. I am enthused about Guanajuato, in part because a very good Mexican restaurant that I frequent regularly here in Minnesota is staffed by a bunch of folks from a village near Guanajuato.

I am looking for advice, suggestions, pointers, warnings, etc. from the old hands. Anything that is "can't miss" or "stay away from" would be helpful.

Muchas gracias!