Cecropterus pylades indistinctus
Subspecies indistinctus was named by George Austin and John Emmel in the 1998 Systematics book (pp.501-2). The type locality is Boiling Springs in the Laguna Mountains of San Diego Co. They say it flies from Baja through California and into Nevada, with a single brood in May and June. I've seen it well into July at higher elevations. Formerly Thorybes pylades indistinctus, the name of the genus was changed after a genome-based phylogenetic overhaul was done on many of the skippers. See "Genomes of skipper butterflies reveal extensive convergence of wing patterns" online here.
This butterfly is widespread, and uses several common legumes as host, such as alfalfa, clover, and false indigo.