It's a little out of your desired area but how about the southern Los Padres National Forest? You could plan any number of hikes into the Sespe Wilderness from out behind Ojai/Santa Paula/Filmore of Hwy 126, 150 or 33. You could even start from out by Frazier Park or Pyramid Lake area off the I-5.
I'd assume the Angeles National Forest has some overnight opportunities as well but I've never hiked there so I can't give you any specifics.
Another option is the Santa Monica Mtns behind Malibu. I've day hiked some of these trails but I understand there's some opportunities for overnight trips. Reliable water sources might be a little spotty though.