I've been riding for 20+ years now. For the first 8, I wore full leathers, and a full face. Summers were brutally hot, most especially when your stuck in traffic. Even just sitting at a red was unbearable. Some friends suggested stop wearing full leathers, and switch to a shorty/beanie style helmet. Having been so used to my gear for the last 8 years, I was pretty apprehensive. But I was pretty comfortable and confident with my riding skills. I decided in the 9th season of me riding, to wear a little less. Bought my first beanie, and just wore jeans and a leather jacket or vest, boots and gloves. Man, that made a huge difference in comfort. And I've been wearing the same gear for the rest of the time. I've even switched to wearing the Icon Truant boot/shoes. All the protection of regular boots, but much lighter, stylish, and more importantly ventilated. I'm currently wearing Akoury beanie helmets (a matte, and a carbon fibre). Very comfortable. Very ventilated. And great on hot days. Plus, it looks better on a cruiser. ;-)
Some people are still apprehensive about wearing open face helmets, and I wouldn't force it on anyone, especially new riders. Get confident in your riding skills, get some experience, then when your ready, ponder on switching to an open face. I can only imagine how hot it gets in Arizona. Btw, I do have an HJC IS-17. But I only wear that when the weather gets too cold for open face (I'm in Canada), or if I'm riding on the highway (I do mostly regular roads, no faster than 45-50mph, the scenic route). It is pretty comfortable, and good ventilation. Mind you my head is only a large size. It does feel a little awkward having my whole head covered though. lol My peripheral vision isn't as good as with my Akoury. A note though, the wind gets pretty loud at higher speeds, so I wear plugs on long runs. But even with full face helmets, it only muffles the wind a little bit. Some people actually wear plugs underneath those too.
Good luck on your riding test, and the helmet hunt. :-)
2002 Vulcan EN500C
Dyna mufflers mod
Reupholstered leather seat
"One of the things I love about riding...she never complains of a headache."