I have been to quite a few Mexican places in the valley and I keep going back to Taco Mex. It's the best I've been to so far. The area definitely looks kind of sketchy but the food makes up for it. Bonus points for being open 24/7. Keep in mind that during the later hours it's more likely you will have to order in Spanish. Seems the English speaking workers usually have daytime shifts from what I've noticed. Also, BoSa donuts next door has really great fresh donuts if you're in the mood for dessert.
P.S. This is a review for the location on Glendale Ave, I have not tried the location on Camelback.