I can't think of any Dominican restaurants off the top of my head... but if you are looking for general Caribbean flavor there are tons. I used to frequent El Meson, a Cuban place, on University between Kirby and Morningside.
Doing a quick Google search, I found the following:
La Dominicana
Capriccio
Let me know how they are! I go back to Houston (my hometown) a few times a year and after few weeks I get tired of Tex-Mex.
And Fiesta is generally the best large supermarket for Latin food...