Hi Josh!
There are herds of us here. I am up in the San Bernardinos, along with Kurt and Ann on the other side of the mountain.
There are bunches in OC, as well as a couple farther south in San Diego way.
Canyon Country, the Valley.. all over the area.
We even have a Victim, er, member in Tehachapi!
Lake Casitas is the formal So. Cal.
rally, but we often do spur of the moment things .. because we can.
The mountain Campgrounds will close in a couple weeks, but the ones farther down stay open all year.
I have a couple favorite places "Down The Hill" I frequent in the winter months, and am planning on a trip to see a few San Diego county parks that stay open year round. They look booked but it is slowing down.
For a quick trip close to home in a nice park, try Canyon RV Park. It's not really an RV park, it's the old county campground that was there in the wetlands just this side of Yorba Linda. Featherly Park, I think it was called.
The owners have fixed it up nicely, and all sites have full hook ups, but it is NOT a stack them on top type RV park. It's right where the 91 and the toll roads meet. North side of the 91.
Just down the 91 to the east is Prado Dam and there is a county campground there, on the watershed. Danged if I can remember the name .. OOPS. I have never stayed there, but for a quick trip, it looks sort of OK.
Any campground with the urban limits will have it's faults :-P.
I also go to Applewhite, in Lytle Creek, or Bonita Ranch Campground in Lytle creek (Private park, sort of funky, but good for the winter months)
If the desert is more your style.. heck, pull up anywhere. LOL! There's Lake Silverwood, open year round, and just down the road from that is Mojave Forks (San Bernardino county run)
I am not familiar with a lot of the parks off the Grapevine. Carol can tell you about those.
My absolute favorite place to camp in So. Cal is a private campground in Crestline. It's called Camp Switzerland, and the non hook up sites are to die for. Lush and on a stream, with Lake Gregory right across the street, if fishing appeals to you.
No dogs over 25 lbs allowed tho. sigh.