Ham radio frequencies
The Mt Lowe repeater operates on a frequency of 147.36 Mhz. A CTCSS (PL) tone of 127.3 Hz is required to access the repeater. The repeater does transmit PL. It is located 2624 feet above sea level at Mt Lowe near San Luis Obispo. This is the W6FM repeater system.
This repeater is linked to the Williams Hill repeater which should give solid coverage from Chular, just south of Salinas, to Paso Robles. It operates on 146.73 MHz with a CTCSS of 127.3 Hz.
That's about 125 miles of HWY 101 North of Pismo!
I'm not sure where you might pick it up from the I-5 Corridor, but I suspect the Mt. Lowe repeater would be accessible on HWY 46/41 near Cholame or Shandon.
Again, Mt. Lowe is easily reachable from the beach and sand dunes.
Coming from the South, the W6OBB repeater in "Sunny Santa Barbara, Tower of Power", 147.000 (+) 131.8 Broadcast Peak, Santa Barbara County. I hit it easily from the dunes and have talked to people as far South as Thousand Oaks.
Simplex
As noted by Cruiserdrew, I'm suggesting the "NorCal" simplex frequency, 146.46 for the majority of the during event communication.
KI6TLC