If you are new in town Valle Luna is a must stop for some great mexican food. They have a few valley locations and will not disappoint.
The Sonoran Todo (Appetizer) is a platter of Mexican fried delights and can be shared by 2-3 people for your MEAL. Its a great deal and super tasty. The Pollo Fundido is also a must and can also be split as it comes with rice and beans.
The atmosphere is typical any mexican food spot, so pretty much out of date with several "team" photos of teams they support lining the walls. The service is usually pretty good as well, but its the food that makes this place a must visit.