This was photographed on a Barbatos Cherry shrub at Resaca de la Palma State Park around 10:30AM. My guess is some species of the genus Centris (initially I also considered Anthophora sp, but pictures from the Kaufman Insect Guide make me favor Centris). I don't have access to a Bee Key so I am posting here. Again, I guess Cetris sp. based on the lack of dorsal markings on the yellow hairy thorax; the large, hairy back legs; solid yellow head; shiny dorsal abdomen with a hairy lateral and ventral sides (see second and third images. It looks like the shiny black dorsal part is a scleritized cover that is not connected to the hairy black abdomen); and distribution range - southwest deserts and mention of liking palo verde and desert willow. While it was not on either of these plants, we do have palo verde here so the habitat and range kind of fit.
Thank you for taking time to consider identifying this bee for me!!!