That snake definitely has splendida in it, but it looks like it has too much yellow and is too clean to be a "pure" desert. I've seen some from the I-10 area north of the Chiricahuas that have lots of yellow, but not quite like yours. The desert king intergrades naturally with the Cal king north and east of Tucson, so this could be a natural intergrade. Knowing Bill Gillingham, I'd say this probably is a natural intergrade, but ask him, and I'm sure he'll tell you.
Here's one from south of Tucson with the typical "dirty" coloration....

Another with more black and very thin banding from the same area....

Ventral view of that snake...

Also, check out the blotch sizes and number to help decide, although there is bound to be a lot of variation.
Yours is a very pretty snake, btw, and I'd like to know how it came about, as I'm considering working with Cal x desert intergrades someday.
TC