i'm in SoCal too and weather wise it can be fairly unpredictable. but one thing is certain no matter what time of year it is always cold or pretty cool at night. i also go all over the place, yosemite, mojave, etc etc at all times of the year. so basically i do want something that insulates and a regular lightweight bivy ain't gonna do that much good. so now i'm back to looking at survival bivy/bags. i was considering the LAND/Shark survival bag but its a bit heavy. so far, the adventure medical kit emergency bivy is pretty lightweight and cheap @$20.00 so it looks pretty good. but that Land/Shark bag is a really good survival bag and only about 20 bucks more. anyone ever use the land/shark?
http://www.land-shark.com/