Hi Marie09,
Lisa got all the main points there. August is a great time to be here for hummingbirds, and everything else. September is also good for hummingbirds, but the peak tends to be the second half of August, and the overall birding is better then, as there are more summer birds still around. The bottom line is you won't be disappointed coming any time in August or September.
A couple of sites to add: Madera Canyon has excellent bird feeders at all three lodges (Santa Rita Lodge, Madera Kubo and Chuparosa Inn), all of which allow the public to view. There are also feeders at various businesses in Summerhaven on Mt Lemmon which give access to the higher elevation species such as Blue-throated and Broad-tailed.
In the Sierra Vista area, definitely visit Mary Jo at Ash Canyon B&B (
www.ashcanyon.com) which is the best place for Lucifer Hummingbird, as well as a memorable all round birding and hummingbird experience.
Higher elevation species can be seen at Beatty's Guest Ranch (although the White-eared and Berylline have been absent the past couple of years).
Battiste's B&B (
www.battistebedandbirds.com) is a great place to watch hummers. Give Tony a call in advance.
Ramsey Canyon Inn and the Ramsey Canyon Preserve both have hummingbird feeders.
SABO (
www.sabo.org) does hummingbird banding events at San Pedro House, mostly Black-chinned Hummingbirds.
In Patagonia, visit the Paton house for Violet-crowned Hummingbird. The Patagonia-Sonoita Creek Preserve also has feeders out.
Don't expect to see Plain-capped Starthroat as it's a big rarity, but it has been seen at Ash Canyon, the Paton house and Montosa Canyon in the past few years, so you might get lucky.
Final thing to add, but an important one. All these amazing bird feeding sites rely on donations to continue. Please make sure you make a donation to help keep these fabulous birding havens open to the public. Thanks!
There's lots more info about birding in SE Arizona on my
Arizona Birding Website.
Hope you have a great time!