and san diego, forget LA
As a native Angelino who spent 13 years living in San Diego before moving to Singapore, I'd second this recommendation. LA does have a lot of interesting places to visit, but you need to know your way around, you pretty much have to drive, and it doesn't lend itself to purely "touristy" things.
Unless you've got your heart set on doing the Hollywood Blvd thing, or you're a serious foodie who knows what's hot in the LA restaurant scene, or you're really into museums, you'll probably have a much better time hanging out in San Diego. The beaches are generally better, it's a lot smaller, and you've got Sea World and the San Diego Zoo. If you're a Singaporean citizen, you've also got San Diego's answer to Johor Bahru right over the border (or is JB Singapore's answer to TJ?). And if you're a wee bit adventurous, continuing south for about an hour to Ensenada is a nice way to experience Mexico (don't hang out in Tijuana). San Diego will also be cooler at this time of year, although still fairly warm.
Nice places to stay in San Diego would be Shelter Island, Mission Bay, Pacific Beach, or La Jolla. Downtown near the Gaslamp Quarter can also be fun. San Diego is about a 2 1/2 hour drive south of LAX, so it's not too far away. You could also break your drive in half and stay for a day or two in Anaheim visiting Disneyland.
As for LA itself, Marina Del Rel is OK, but as far as beaches go it's not all that great. It's more of a shopping/dining area. The beach at Playa Del Rey is better, in my opinion. Venice beach is, um, interesting. I like the beaches further up the coast at Malibu, Zuma, or Leo Carillo, and drives through Topanga or Las Virgines canyons or along Kanan/Dume road are nice (my commute from Calabasas to Marina Del Rel used to take me through Las Virgines canyon - a lot nicer motorcycle ride than the CTE ;-).
Have fun!
