Me gusta Patron's! Just so happened to drop in on a Sunday for the buffet at Monroeville. Ample selection of tex-mex on the buffet line. Very reasonably priced at less than $9 per person. Friendly staff and a never ending glass of sweet tea as the staff are very attentive.
Fox Chapel has the same service but I don't think there is a Sunday buffet. But service is great, very little wait time to get your food, and it's piping hot and fresh! Wash it all down witih a margarita!
If they had homemade tortillas, this places would get a 5.