Samk,
Phoenix is a great place to grow orange and other citrus varieties. There are dozens of choices when it comes to oranges and they fall into three basic groups - navels, Arizona sweets and Valencias.

Navel oranges are easy to peel and are seedless. They can be juiced, but the juice must be used immediately because it turns bitter quickly. The fruit production is not as good here in AZ as it is in CA and homeowners are often disapointed in the number of oranges on each tree. Because our summers are hot and dry it is common for the trees to drop immature fruit in June (called June drop). There is nothing we can do to prevent this.

Arizona Sweets refer to a group of oranges that grow vigorously with sweet flavor and abundant juice. They ripen as early as October and include varieties such as Hamlin, Trovita, Diller, Marrs and Pineapple.

Valencias are also sweet oranges that typically ripen in February or March. They produce a high quality juice with deep orange color.

When planting citrus it is important to loosen the soil in a wide area where you intend to plant. Then remove soil where the tree will be placed only as deep as the container, but a little wider. The level of the soil in the container must remain level with the surrounding soil. Backfill with native soil and water well.

It helps to create a berm about 6 inches tall and wide around your tree at the edge of the branches. This will result in a basin that you can fill with water from the hose or place emitters in. Adding a 3 inch layer of organic mulch will slow evaporation and keep the soil cool during the summer.

Citrus need to be watered deeply (to three feet) but infrequently. Of course when your tree is newly planted it will need water more often for the first few weeks, but eventually you will only need to water once a week in the summer and once a month in the winter.

You will probably need to protect the trunk of your tree until its branches grow enough to shade it. Use a latex paint and dilute 1:1 with water. Any color will do. Or you can wrap loosely with cardboard being sure to allow for air circulation.

I've listed a link to more information on growing citrus. You also might want to attend the annual Citrus Clinic hosted by the University of Arizona. There is one on the east side of Phoenix and one on the west side. http://cals.arizona.edu/maricopa/garden/citrusclinic.htm

Here is a link that might be useful: Citrus Information

There is no better site than this one and they only stock trees that grow here because they are here.

Take a close look at Trovita and Macetera as they are easy to grow here and they grow fast.

Here is a link that might be useful: Greenfield Citrus Nursery

One thing that hasn't been pointed out is the selection of rootstock. The longest consistent performer for citrus here has always been Seville Sour Orange for standard size trees. Both John (at Greenfields) and myself grow our trees on this rootstock.. Our trees grow here because we "Are Here" also.
There is no real botanical name of "Arizona Sweet", Sweet Oranges as mentioned before have been called Arizona Sweets because there's been so many of them in the valley (years ago) mostly Trovita's.. but give good consideration to the Seedless Midknight Valencia. They handle a wider range of temperature fluctuation

Here is a link that might be useful: RSI Growers

We have Arizona Sweet, Trovita, Valancia and Kinnow(?)Tangelo, Ruby Red Grapefruit. We get way more oranges and grapefruit (only 1 grapefruit tree) then we can eat. We end up juicing most of the fruit from the orange trees. The Tovita makes such sweet OJ, you would swear we added sugar. The Valancia is not as sweet but still very good. We eat the whole fruit from the Tangeloes. It peals very easy and has great flavor - and a lot of seeds.

The grapefruit is fantastic also. My daughter just likes the juice.
After burning up several of the cheap Black and Decker juicers, I bought a heavy duty Bosch mixer with juicer attachment and it will juicer forever with out heating up.

I plan on buying a small freezer just so we can freeze some of the OJ. I hate to see the oranges and grapefruit go to waste.

I think anyone suffering through the summers heat here needs to reward themselves by growing some the fantastic citrus that can be easily grown here.

There are some excellent newer varieties that are suited for the hot desert climate regions in and around Phoenix. I live in a suburb just outside of Phoenix and have several citrus trees that are *thriving* in our desert climate. Trovita is a proven winner, actually does quite well under desert conditions. Some newer arrivals on the scene are excellent choices for the back yard - Fairchild Tangerine, and Midknight Valencia. They are both vigorous in growth habit and excellent producers. I also have Ruby Red grapefruit, and Lisbon lemon.... all are doing quite well. Here is an excellent link for all your research on Citrus. Keep in mind you want to get semi-dwarf varieties... they will still reach upwards of 15 ft but higher than that and you'll have problems harvesting the fruit down the road.

Check out the following two links:

http://www.citrusvariety.ucr.edu/index.html

http://www.greenfieldcitrus.com/index.htm

Between these two links you'll have everything you need to know about growing citrus in the valley. One key note - as tempting as it is to buy the biggest tree for immediate gratification, realize that the larger trees (15 gallon and larger) take much more time to get established. If you purchase a vigorous orange variety such as Trovita or any one of the many mandarin/tangerine varieties, opt for the smaller 5 gallon varieties.... they will establish much quicker, you will get very quick growth (4 to 6 ft in the first 2 years) and fruit by the 2nd year! No matter what size you buy, you will not get a huge crop until a few years after planting! Enjoy your citrus!