Valley fever is very different from hay fever. Hey fever is an alergy, Valley fever is an infection, not nice! It has to do with some bacteria, i believe, that growns in the dirt.
I've been here for 13 years, and I love it. The smog, though is not healthy! If you have other options, like maybe flagstaff, or tuscon, they may be better than the valley of the sun - Phoenix. Flagstaff is awesome!
You can develop alergys to the 'local' plants. Alot of people move here, and they bring the plants from around their house and end up with the same alergys they wanted to leave! So, if you do move here, leave all the rugs, couches, and plants back there. My wife developed alergys to the flora here. I haven't noticed any myself.
The clinic in phoenix suck, in my humble opinion. but that's probably just me.