I've been eating at Chuy's for years - ever since my college days in Tucson. This place is cheap and cheerful - what more could you want? The food is good (I love the California Taco's), the margarita's are fabulous (I love the strawberry one's and the regular one's are so strong they make me sweat!) and it's pretty family friendly. They have great happy hour specials during the week and a full bar.
You can feed 2 people for under $20 bucks and that includes a pitcher or beer AND margarita's. They have free chips, a salsa bar, and an ice cream dispensing machine to boot.
I've used Chuy's to cater corporate lunches before and it's a great deal if you need a lot of food to feed a group with a small budget. The only problem I've ever had with catering is that they forgot to give me my guacamole 3 times in a row...so check your catering order before you leave to make sure you have everything.