I would like some more input, but I found a group of 5 Chaetura Swifts this morning (9:30-10:45am) circling above the "island" and then Talbert Lake at Huntington Central Park this morning. To those of you unfamiliar with the local lingo this is directly north of the Huntington Beach Central Library. They have the nice bulge in the secondaries, and the long thin wings I would associate with Chimney Swift. Although lighting was poor, my photos don't seem to show the pale rump of a Vaux's and the facial pattern seems to match the Chimney Swift shown in Sibley. Size wise they were slightly smaller than the surrounding 3 Barn Swallows.
Sibley posted a nice overview of the comparisons between these two species;