I did my PPL in Santa Monica and have quite a bit of experience in the LA area. Never had any problem with their ATC, seemed perfectly helpful in fact.
Word of advice though, Santa Monica is VERY expensive, and it would be cheaper to fly out of Long Beach. It's not that far to drive, and is loads more interesting. Five runways, B717 and C17 production, UPS base, regional airline traffic etc. If you're looking for somewhere quieter then Santa Monica is definitely not the answer either. Someone told me it's the busiest single-runway GA airport in the US.
Anyway, loads of great places to fly to out there.
Cheers,
-Abracadabra