Down and dirty real Mexican food. Strap on your kevlar vest, use the bathroom (so you don't have to use theirs), and get there before dark.
All kidding aside it's actually quite safe during the day. There are always plenty of cops, EMTs and firefighters getting their taco on for lunch. I think it's a requirement for municipal workers to eat here at least once a week.
The buttered tortillas will absolutely change your life. I have dreams of their green machaca burro.
[pauses to salivate]
They are REALLY busy between 12:00-12:30, so try and get there a little before or after to miss the rush and long line. Or call your order in on the way and pick it up from the shorter pickup line (you can still eat in the restaurant).
Aside from the ambiance, it might be the best Mexican restaurant in Phoenix.