I just went to a great new-ish Mexican restaurant in Tustin. It's on First St (137 W First St., Suite A Tustin) in the same shopping center as The Sandwich Box (which is good, too, by the way). I had their tortilla soup, and it was really a standout. The texture of the soup was very velvety, and it had big chunks of chicken and avocado. They also had excellent (I think homemade) tortillas. They were thick and a little chewy, made with masa, not flat and yellow like you get at a lot of other places. Try it, try it (and let me know what you think!).