Taco Milagro is one of those huge tex-mex chains that Houston has to offer, and of the chains, it is probably the best. While I try to stay away from chain restaurants as much as possible, if I ever have to go to one, Taco Milagro is usually where I end up.
What really sets Taco Milagro apart from the other chains is the quality of the meats that they use. You can definitely taste flavorful beef and chicken in their dishes, which is a hard thing to find today. Their fajitas are what I've ordered every time I've gone, and while they tend to skimp on the accompaniments, they'll happily bring you out some more free of charge. They have a pretty decent Margaritas, but they tend to be on the weak side; I would just stick to the beer. The tortillas are made in house, and you taste the freshness, specially with the decadently large flour tortillas that they have. You should also go ahead and order more tortillas from the start as they are almost certainly not going to bring you enough to finish your fajitas with.
Overall, I would have to say that if you don't have the time to go exploring into the small, family owned businesses, Taco Milagro is your safest bet to satisfy your Tex-Mex cravings.