I am from the bay area, south san jose, and have lived in Prescott AZ for a whole 6 months attending Prescott college. With that I can say the weather was significantly more dramatic than california in terms of heat/cold fluctuation with the lack of moisture amplifying the hotness and coldness of an otherwise mild latitude. Dehydration in summer and fall, freezing in winter. Its a good place if you want to toughen up your inner animal. I actually got quite sick after my first winter there as I was not prepared for how biting it was compared to california/tahoeish winters. (I am from a mild climate so take this with a grain of salt). The town itself is a mix of VERY traditional/conservative types (John McCains hometown), as well as VERY non traditional/ anarachoesque types and artists mainly from the college ,also Arco Santi which is close to there. It is close to Flagstaff which is beautiful, and the grand canyon, as well as Pheonix. Prescott is safe and friendly and has a hometown feel, but is small and isolated. Much safer feeling (to me) and hospitable than parts of Phoenix which is about 1.5 hours away.
Personally, I would chose to live in San Diego, as I missed the ocean in Prescott, being a surfer. Additionally, I would find the culture of san diego more palatable. Nuclear is sketchy, ill give you that, though it may be useful to look into studies of cancer rated in surrounding areas to get an idea of the effects. It is a personal choice based on what you value, where you want to place your family. Fresno and Central Valley/ Yosemite foothills are a great place, but far away from life enhancing culture that San Diego has Id say. There is strong conservatism and water rights power struggle mentality in Fresno, and I do not know many permie activities out there save some awesome and progressive commercial farmers.
My two cents, for what its worth..Maybe go an see in person on a trip. The worst parts of san diego will be the prices, trafific and fire danger. The worst of arizona the conservative biggotedness and exteme heat/cold. The best of both i think i already covered....okay im done..... BEST of luck~!