The foods, the family I lived with there for a few days and the Guadalajara sights.
The San Juan de Dios Market. (I just recently finished the vanilla I brought home from there, which reminded me of my trip every time I baked with it.) The Corona Market in Guadalajara's city center. And much more. My nice teacher at the IMAC Spanish language school in downtown Guadalajara.
I was in a class with about five others, who ranged in age from teens to probably 60's. I loved the fact that la maestra couldn't revert to English to explain things (she didn't speak it well) and that I was able to follow along in Spanish pretty well.