#1. I'd ditch the backpacking plan if you want to stay in So Cal. What's the point, when you can get hotels on hotwire at reasonable rates and eat/sleep/poop civilized?
#2. I'd dayhike a few of the local peaks:
San Gabriels:
a. Mt Baldy via the Ski Hut trail, or if you've been there, Mt Baldy and Mt Harwood via Register Ridge (who doesn't like climbing 2000 feet in less than a mile?

)... 9 miles w/ 4000' of gain r/t
b. Cucamonga Peak from Icehouse Canyon ... 12 miles w/ 4300' of gain r/t
c. The Three Ts loop... start at Icehouse Canyon to Icehouse Saddle, then summiting Timber Mountain, Telegraph Peak, Thunder Mountain, and ending up at the Mt Baldy ski resort parking lot (requires a car shuttle back to Icehouse Canyon TH). 15 miles w/ 4600' of gain (loop)
or if you're dead set on backpacking, how about an overnight?
a. Icehouse Canyon to Kelly Camp (~4 miles one way, 2000' of gain), dump your stuff, summit Ontario and Bighorn Peaks (~2 more miles w/ 1000' of gain one way), and spend the night, and pack out in the morning...be out in time for pancakes.
or if you really want to backpack for a few days, do a few legs of the PCT through the San Gabriels.
Other options in the So Cal area:
1. San Gorgonio, which is the highest peak in So Cal. Between 10 to 20 miles r/t depending on the route. However, this peak might have snow by Nov.
2. Mt. San Jacinto, 10 miles w/ 2000' of gain r/t if you take the tram from Palm Springs
or go totally different, and go to the Channel Islands. You can dayhike, you can stay at one of the established campgrounds, or you can backpack there. I've never done it, but I imagine it's something like backpacking just to camp in one of the developed campgrounds because once the ferry leaves...you're not leaving until they come back for you!