Well, not Arizona heat, but we live in Texas and it get's pretty hot here too. We spent a week not far from Pecos, Texas and the temps hit 115 degrees.
We had no problems with the trailer and our 2011 21fbs came with the 15k btu air conditioner and it had no problem keeping the trailer nice and cold.
We did have a blowout on the tow vehicle, but that's a whole other story. We've gone on 4 trips so far this summer with a trip planned to go to Glacier National Park after labor day.
Enjoy your trailer, we sure like ours.