I find it hard to imagine that 1510 wouldn't reach at least partway into L.A... I can hear it in the daytime here in El Cajon, near San Diego, although not exactly with a very strong signal.
So what is it that prevents stations from being heard much more than several dozen miles, or so it seems? Are the static levels in L.A. up around 250mV/m, or are people not willing to listen to a station that doesn't have a 90dB signal-to-noise ratio? I'm probably about 100 miles away from KNX, but I can hear them with a fairly clear, almost static-free signal here. Also, I can hear KLAC, KSPN, KABC, KLAA, KRLA, KHJ, KFWB, KTNQ, KDIS (but not KTLK due to strong locals on 1130 and 1170), KFRN (but not much at night), KWKW, KMPC, KBLA (although night is usually dominated by KMIK) here day and night, mostly, yet I've heard you (or someone) say some of their signals don't even reach orange county at night. ??? ??? ???