I have been asking the same types of questions since I live in Oregon I don't make trips to the area very often. What I have come up with for my family, kids of 14, 12, 10 is the SoCal City Pass. For $279 I get 3 days at DL, 1 Day at Sea World, 1 day at Universal Studios. Seems like a pretty good deal as 3 day park hoppers are currently listed at $209.
We also bought season passes to Six Flags for Magic Mountain. By buying them around Christmas we were able to get a deal where Hurricane Harbor, a local water park day was included. We are going to be able to use the season pass at another park on our way back upstate in Vallejo.
I have really thought about Knotts as it seems to be getting a lot of love too, but the SoCal pass is currently winning out.
If you have more money than us I would recommend the Los Angeles Go Card. You would have to by park hoppers for DL separately, but for 5-7 day cards you can get all of what has been mentioned. Check it out at mousesavers.com.