My choice was the San Angel Inn- not so much for the food but because it is so pretty of a setting that I think that someone who has never been to Disney before would really enjoy the theming, especially with a seat at one of the tables by the water!
I voted for San Angel Inn mostly for the ambience as well. I've always found the food to be good, but the ambience is really beautiful. I always go inside the Mexico pavilion to look around, even if I'm not eating at the restaurant.