I live on the Ocean Front Walk in Venice, CA. I have visited San Diego, and LA is way more fun. There will be traffic, but if you plan it right you can minimize the pain (i.e. don’t travel very far at all during rush hour, avoid the 405 Freeway as much as possible).
If you go to LA, you have to visit Venice. It’s pretty cool, and the best part is that once the novelty wears off (seen enough freaks, bought enough hemp necklaces and imitation sunglasses, Bob Marley t-shirts) I could direct you to a few cool places I’ve found now that I’m a local. If you walk a few blocks inland, there is a drag called Abbott Kinny that has my favorite tapas restaurant “Primitivo” and my favorite bar “The Other Room.” None of which are worth travelling for specifically, but if you’re in the area you should check out.
Just north is Main Street, with amazing bars and restaurants, and leads into Santa Monica, with the same, including the 3rd Street Promenade, which has cool break dancers and street performers.
Also, when you go to Hollywood, there are alot of bars off the beaten path worth checking out, like Beauty Bar and Star Shoes.
The Getty is awesome, when I was there, I stumbled into a Rembrant exihibit (didn’t know it was going to be there . . . it was amazing).
Then there is Malibu, which is northwest of the LA beaches. You can watch some awesome surfers and drink cocktails right on the water at Dukes.
Don’t waste your time with the Tarpits, they are boring and there’s nothing near them to make it worth the trip. There’s nothing to see north in the San Fernando Valley.
Overall, my opinion is that an LA trip should include Venice, Santa Monica, and Hollywood, and Malibu.
If you’re interested in any of the above places, I’d be happy to find links (out the door at work or I would have done it already).