If you're looking for Mexican seafood, I'd say MPH gets the nod over other joints such as Acapulco Bay (S. Scottsdale), San Carlos Bay (CenPho), or San Diego Bay (Guadeloupe).
The place has a bit of a rep for crab enchiladas (there was a blurb in Gourmet a few years ago), but they may be one of the more bland things on the menu.
I'm going to second the idea that the shrimp dishes are a great way to fall for this place on the first visit. The camarones culichi are awesome, with a tomatillo sauce that should be distilled into bath salts. Snapper veracruz is delicious if you're looking to test one of the more typical preparations.
Oh -- This place isn't really that parking-sketchy (especially if you've experienced the Ranch Market demo derby up the street) and they have their own lot right in front.