I moved to Katy 4 years ago from south houston. There wasn't a corner you could turn to and hit a great Mexican restaurant. Unfortunately it's not the same here in Katy. I have yet to find a great taqueria style restaurant. And even taco trucks are hard to come by. Here are my two recommendations; TexTaco on Morton and Katy ft bend (near the new heb) I go there mainly for breakfast tacos as that is what they are known for. For street style tacos I go to Taqueria Tacos El Paiza (Food Truck) on west green and park row. They are times the food is really good and times it's just fine.
I'm really wanting a taqueria style sit down restaurant similar to Taqueria Del Sol in south houston. When the day comes and I find that I will let y'all know.