Sylvia's Enchilada Kitchen

This unassuming restaurant may not look like much from the outside but it's consistently rated as one of ten top spots in Texas for an enchilada. Sylvia's has been in business for more than 20 years and regularly wins awards.
There's a full Tex-Mex menú here but the specialties are enchiladas -- Tex-Mex, New-Mex, and Mexican style. Prices have gone up in recent years but are still affordable considering the quality -- you are looking at $11 for a plate with two enchiladas, beans, rice, and "chili gravy", which is a Tex-Mex classic.
For $14 you get a plate with three enchiladas -- which honestly is so much food you won't feel too good afterward.