There are a lot of good hikes in the "greater Los Angeles" area.
The Santa Monica Mountains are lower elevation and offer some good hiking. See
http://www.backpacker.com/february_2008 ... 080?page=1 for one example of a hike there. See also:
http://www.latimes.com/news/obituaries/ ... 1813.story
The Gabrieleno National Rec Trail in the San Gabriel Mtns is a good one. It can be done as either a long one day hike (25 miles?) or an overnighter.
Joshua Tree NP has some good hiking, but they do get snow in the desert sometimes, so you'd have to have a plan "B" in mind if it's set to snow around the time of your hike.
The Santa Ana Mountains in Orange County offer some good hiking.
Catalina Island has some good hikes.
Just some ideas,
HJ