I realize that southern California is well outside of the native range of this species, but I am 100% sure of the identification. Note in the photos the pattern of irregular light blotches in a dark background on the anterior dorsum: opposite the pattern of a gopher snake. Also has large, distinct square black markings on the ventral surface. Blotches on the posterior dorsal surface large, light-centered, with a shaded dark border, elongate black-edged light spots on the side of the neck.... Looks like an anerythristic morph of a corn snake, somebody's dumped pet. I last drove this road on 2 August, at 17:00, and I'm sure this snake was not there, so it's well under a week old, but very skinky condition indicates it's over 24 hours. Falls into that gray area.