You will get LOTS of responses to this.
I work on the southwest side and there are tons of them. Of course, some of them I am scared to walk in to
Aranda's on Military is good. Lupita's (on Culebra I think) used to be good but something happened and their prices went up and the food went down.
Lisa's used to be on Commerce but they moved, very good mexican food.
There is a place on Hwy 90 and Military, right on the access road, I can never remember the name of it but it is in front of a hotel and next to Taco Cabana, it is very good and gets packed at lunch time.