Fuel City on Industrial/Riverside has the best tacos, my fave is the Pastor(haven't tried their breakfast tacos).
The Taco Joint on Peak between Gaston and Live Oak has great breakfast tacos and the Disaster is better than the Bob Armstrong at Matt's
The old Matt's Noplace was an excellent mix of TexMex and cowboy range food. Matt's ElRanchero is not quite what it once was since he past, one of Dallas' greats has left us.
La Calla Doce has the best Mexican seafood, I love the ceviche.