Check out Samba Grille downtown in Bayou Place. Walking distance from the theater, and their Latin cuisine is drawing raves.
By Texas standards, Houston isn't a truly strong BBQ town. We have some good places, but none that I consider among the very best in the state.
We do have some great places for Mexican food. Pappasito's is certainly OK, but it's not the best to be found.
My favorite spot for Mexican food is Pico's on Bellaire; they specialize in more traditional Mexican dishes as opposed to Tex-Mex. Hugo's in Montrose is a more upscale version, and an outstanding restaurant that's building a national reputation.
But if you're focused on Tex-Mex, consider Lupe Tortilla if you love fajitas, Sylvia's Enchilada Kitchen (for enchiladas, of course) and Tampico if you're in the mood for Mexican seafood.
Sylvia's Enchilada Kitchen