All of the major Phoenix TV stations are on South Mountain in Ahwatukee, and present a moderately strong signal at your location. You do have a small peak that causes some shadowing between the transmitters and your house, so an attic antenna isn't recommended. You should do very well by using a Winegard HD-7694P or an AntennaCraft HBU-33 mounted on your roof, aimed at roughly 180 degrees as measured by your compass.
When installing your antenna, you may find it easier to use an eave mount, which will mount on the side of the house, but have the antenna peek over the highest point of the roof. Roofs in the Valley of the Sun are absolutely no place to be in summertime.
Be sure to use all high-quality RG-6u coaxial cable, preferably BLACK insulation cable, as the white cable doesn't resist Ultra-Violet light well, and will break down fairly quickly in the sun. Black RG-6u can be painted, however, if aesthetics are a consideration. If you shop carefully, you will find everything that you need for your installation for less than $125.00
Here are links to the equipment:
http://www.winegard.com/kbase/upload/HD7694P.pdf
http://www.antennacraft.net/pdfs/HBU33.pdf
Here is a good installation manual:
http://manuals.solidsignal.com/AntInstallGuide.pdf