Serrano's is one of those Mexican chains that just does it right. While it is slightly dirty and the staff can sometimes be lacking, their food more than makes up for it. It tends to be slightly on the spicy side so make sure you are prepared for that before ordering. I personally like this location over some of the others in the area too because they are more consistent with their food.
I sincerely miss being in AZ because of Serrano's!