Question
i have a 6 foot wall around my back yard  my area is  is just west of palm springs avrage rain fall about 5 inches  and heat up to 120 and over in the summer  i need a wind brake and something to hide the wall from my dog who jumps over it a small dog at that

Answer
My desert home, The Great Basin, actually is tougher on plants because it is a "cold desert"...you, in Cochella Valley/Mojave get a lot hotter, but its the frost & snow that destroys plants quicker.  (It just snowed here on Tuesday!!)

That said, I think you have more to chose from for screening.  Here are a few that might work:
Himalayan Blue Bamboo
Golden Bamboo
Buddlea - Butterfly bush
And for something bigger, my lists say that Scotch pines should grow there, as well as Sago Palms.

For an additional list of plants that others have reported sucess with in Palm Springs, try this link (sorted by your zip code):

http://davesgarden.com/pf/zipbyzip.php?zip=92264

Unfortunately, they are not sorted by size/use - but you can click on the links to see a picture & description of them.

If you want to check out some other plants, here is a list just for the Cochella Valley region:

http://www.cvwd.org/lush&eff/lsh&ef45.htm

Two other sources of ideas: I always try and see what other folks in the neighborhood have tried, too.  Hey, its free to look at their yards from the street!  And, #2: The local nursery.  They want your repeat business, so they won't usually sell you a plant that won't grow in your area.

Hope it helps!  -Marc