In looking at it, SoCal is covered on the SNA feed, part of the EMT feed, the PSP feed, the RAL feed, and the RNM feed.
The KEMT feed does not have any SoCal frequencies on it. Of the two sectors covering EMT, 135.05 is at Burbank on the other side of Verdugo Hills, and 125.5 is at Ontario on the other side of Chino Hills. No line of sight possible for me for either. In fact, aircraft out of EMT usually can't contact them reliably until 2000 MSL or so.
I haven't tried any of the other SoCal frequencies, though.
The 3rd frequency is 123.3, which is the practice area CTAF, and sometimes Unicom for an FBO in Hawthorne and one in Santa Barbara.
--Carlos V.