A long time Tempe staple, Restaurant Mexico is true gem.
This is not Northern Mexico/Sonoran food. These are from family recipes from the region around Mexico City. All of these reviews claiming inauthentic food are from dumb know-it-all's that have never had anything but sonoran style.
The food is spiced very differently. Words like quesadilla refer to something entirely different. Once you let go of your filibertos based preconceptions you are in for a treat!
I usually recommend the #5, #6 or Clare Burro for first timers. Either of the combos will treat you too the incredible chorizo. This delicately spiced meat is much more subtle in spice and more finely ground than its boarder land counter part. The #5 will offer the chorizo atop a tostada, while the #6 will present it on their sope. Here a sope is sort of like a tostada with fried masa instead of a fried tortilla. Finally the Clare Burro is a whole bean burrito with avocado, an amazing house green sauce, and the always spectacular white Mexican cheese.
Restaurant Mexico is not a gastronomical hipster adventure. It is not a sonoran greasy spoon. Restaurant Mexico is deep central Mexican comfort food. It is your abelule's kitchen.