I figure i would jump in here

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I lived in SoCal as a child & have returned for "trips" 20+ times in the past 20 years. I've seen SD, DLR, Hollywood/USH, Yosemite/Sequoila, & now SF discussed.
Most (or all) are doable on a 8/9 - 8/22 trip, but I think you need to decide what you want to do & how important each are.
If i was planning this for me (or for a close relative), I would consider the following:
- Fly into SF. Rent a car. "Do" SF for 2 nights (2-3 days).
- Drive to Monterey (one night).
- " " Big Sur/Hwy 1/Hearst Castle (spend night in Cambria).
- " " Morro Rock/SLO/ (then either SLO winerys - inland....or Pismo Beach)/Santa Barbara/ Hollywood. (hotel next to US)
(May want to spend the night in Pismo or SB if you want this more leisurely)
But (imo) stay at hotel next to USH on Wed. 13th. Visit US Thurs. till after traffic dies down. Drive Thurs night to SD.
- Thurs night/Fri/Sat (night) San Diego.
- Sunday morning drive leisurely back to DLR (stopping at Capistrano/Laguna/Huntington/ beaches etc.)
- Sun night/Mon/Tues/Wed/Thurs - DLR.
- Friday fly home (from LAX or SNA or Ontario)
IMO - Yosemite/Sequoilla / SF & SD is TOO much driving & backtracking. I would dump one (& my recommendation dumps Yosemite etc.)
Also, I didn't include in my itinerary above.....but with 18 & 20 y/o...a half day poking around Malibu/Santa Monica/Venice area is "something to see" & talk about. Malibu & Zuma beaches aren't talked about alot on this board, but are world famous for lots of things.....some that 18 & 20 y/o boys might be interested in.
Main thing i want to encourage is that with 2 weeks, you can see ALOT of California. But:
- Minimize the driving (thus one way down the coast)
- Do DLR last.
- SEE SF/SD but also SEE the Central Coast.
Here's a post (with links) that discusses this type of trip....also look at SpartanGirl's TR (with lots of pics).
http://www.disboards.com/showthread.php?t=1669293
Have fun planning a trip to Cal. & Walt's Park.