Agree w/ kef - you can't get to all the places you want w/o a car.
If you want equi-distance from either Universal or Disney (which are a solid hour apart or more) it would be near the airport but not squat to do there.
You'd need to look at the Marina or Manhattan Beach at that point. But another place that people stay at in the Santa Moinca area is the Doubletree hotel (Hilton chain). It's usually more reasonable in terms of $$ than the Sheraton.
Just curious - why don't you drive in LA? It's not as bad as made out by overseas publications etc.
Enjoy your stay. Cheers.