We have a 31' Class A with one air conditioner and it does fine for us. I think it depends on how it's vented. We've got vents in the bedroom, so it keeps things plenty cool. Using a fan if you feel like the air isn't getting moved around enough would help.
If the trip to look at the rig isn't going to break the bank, I'd go look at it. Heck, if the rig's in Arizona, you'll know pretty quick how it does!
Good luck!
On the road and happy with Jed and Tilly, my four-legged camping buddies
2015 Thor A.C.E. 30.1