59 Diner is an American restaurant par excellence! With retro-style red leather booths, waitresses in kitschy uniforms, and unlimited coffee, Diner 59 serves simple all-American food at reasonable prices. I'd recommend the chicken and waffles...you get two fluffy waffles covered in maple syrup and fried chicken wings.
Houston is a big city, but it shuts down pretty early. I arrived at IAH at 11 pm and was not out of the concourse until half-past. We hopped on 59/69 and by downtown decided we needed some tacos. The dining room of this outpost of the fast food restaurant is open until midnight, with the drive-thru open 24 hours. When it's not too hot, there's a nice patio out front where you can watch Houston bustle by. Taco Cabana used to be famous for its extensive $1 and $2 tacos and burritos, but now it mostly sells "meals", which offer more food but are not nearly as fun. My go-to the past few years has been the street tacos, which are often on sale for $5.99. It's three tacos of your choice, beans and rice, some guacamole, and a few of their excellent tortillas. Though the cheap meal is gone, the fairly big salsa bar is still there. Yum!