I won't be a lot of help in terms of contacts beyond what Blindzebra has already give you, but I can tell you that you want to start working summer games ASAP so that you can get to know some of the other refs in the area.
I moved to the Phoenix area last fall, right before the season started (I happen to live in Mesa also Power & McKellips) and was somewhat behind the eightball. HS ball is done with a permanent partner. No one knows you and you don't know anyone so it is hard to hookup with a partner that you want. Also as a new official you will be rated as a "5" or transfer official and will have to get re-rated during the fall (they have a scrimmage that you work at).
Rather than bore everyone with this, email me (
[email protected]) with your phone # and a good time to call and I'll give you the skinny.