After researching on just about every topic brought up on this board, as a newbie to the area, perhaps I can offer you another viewpoint to your questions.
AC/Power. We keep our house at about 78-80 while we are in Phoenix during the summer. We also have a pool. Our largest bill yet was just over $325. In our home in Minneapolis, our highest electricity bill this summer (2011) was about $375. Our home in Phx is maybe a bit larger than in Mpls, but our home in Mpls is 2 stories and runs about 6 computers 24/7. We also keep it about 72 to keep the indoor air drier. The peak usage in a typical July AZ day can run up to 100kwh, a lot, but if you have SRP, just keep the pool, AC, microwave, washers off during the 3-6pm peak.
We have CT's (current transformers) for monitoring per circuit electric use (we are techies). The biggest hog is the AC unit, then the pool pump, followed closely by the AC blower. Also worth mentioning to a new resident. The utilities require a deposit (like $80) despite how good of credit you have. A little thing that kind of took us off guard. Guess it just reflects on the area.
RE: the statement about using solar panels, you're not going to get enough power to really make a difference. We are all for solar, but the 10-20 year payback isn't cost effective. It is more efficient to improve the insulation of your home (unless you have money to burn). The typical larger panel you will buy for a home is maybe [advertising] 233 watts, so you'd need several dozen to run an ac (about $600 per panel). Most people that have solar use it to heat their water. Get a solar pool cover for winter, cheaper and you'll feel good having something solar in the VOTS.
Also, buy a remote programmable thermostat. We can log in at any time and set the temp we want (Android, iPhone, web). Very handy and you can easily program settings via a web browser.
When our AC went out one time, the house got to 98. Candles started bending and I noticed some yellowing in a few cotton items. When the AC was repaired, it took several hours to cool the house and the contents inside. The 3 degree rule as someone mentioned is so true for efficiency (keep your program set for no more than 3 degrees difference when in house). We've been in-house about 3 weeks each month this summer.
Regarding the monsoon. As a midwesterner, the biggest yuck is the dust. Even if there isn't a dust storm, there is still dust. I've been there this summer for 3 of the 4 significant ha****s. The first one on July 2 (I believe) was horrible. Dust everywhere, even inside with doors shut. Prepare to clean your pool often (best to have a pool with a sand filter for this - the pool guy says) and ALWAYS change your air filter every 30 days. MERV 8 rating is what our AC guy gets us.
As far as scorpions, never seen one. Everyone in the "know" that I've talked to has said the same thing. You can't exterminate scorpions because the only thing that kills them is to smash them. Instead, you exterminate their food source. Cockroaches, spiders, crickets and even small rodents. Also, the news last week had a story on the outbreak of scorpion stings in the valley. 1,600+ in August alone. They say the hot temperatures are to blame. Ask your neighbors if they've seen any. Ours have not, friends on the other side of the mountain in Ahwatukee have. Get a black light flash light and go around your home at night. They love cinder block walls.
Don't be alarmed if you get the stray large cockroach. Be alarmed if you see little cockroaches. The city of Phoenix sprays their sewers to "control" the cockroach population. I'm told by a city worker that really all this does is move the cockroaches to a different part of the sewer system. They will come up through drains at times, so if you see a big one in your house, you may see another or a few more around that time. Likely they will be dead - or almost dead, then hopefully they will be gone for a while. Keep your house clean of crumbs and food and sugar well sealed. If you get a problem, call an exterminator immediately.
Never seen a black widow or tarantula. Sometimes these little black spiders with an orb body show up in the pool, but I don't know what they are. I hate spiders more than anything and really don't want to know. Snakes either, but we do see a lot of lizards and some praying mantis.
Our house is in a newer development in S Phx by south mountain (Baseline/24th st). South Phoenix isn't the best, but our development is newer and clearly separated from the nearest dumpy area. From what I've seen, you will see nice/poor areas next to each other in various areas throughout the city. I'm personally more afraid of areas in Minneapolis than anything I've seen in Phoenix - so far. Never seen a gun there either, but have here (pointed in someone's face as we drove by).
We've been going to Phoenix for the past 10 years (6 to the same house) and decided to buy this year when the opportunity came up. 1900sf, 14 years old, $95k. Taxes are around half (proportionately) of our place here in Mpls (where our homestead is). I don't remember how much car registration was, but the emissions test was $27.
A little OTT but worth mentioning. If you're a liberal from a blue state like we are, be prepared for the bit of culture shock. Sometimes you may have to grin it out. So far, it's harder there to co-exist among conservatives. Just saying ...
Hope this helps out a bit. Good luck with your new journey.