Need tips on what we can do and how to best split the time between the 2 cities. We have a 4 yr old along...so have to consider what will interest her. No aversions to driving and would in fact want to drive down to SD. Any suggestions would be a start for me!
Thanks so much

Are you going in the summer time? Do you want to spend time on beach?

I would suggest:

2 days in LA area
- Go to the Getty Museum
- Hang out in Westwood area (near UCLA).
- Visit Hollywood (just because even though people here will tell you it is not worth it)
- Maybe visit Venice Beach (although not everybody enjoys it)

2 days in Orange County
- Go to Disneyland for 1 day (that is all a 4 yr old needs)
- Go to Newport Beach or Laguna Beach for the day

3 days in San Diego
- Go to the zoo
- Spend a day in La Jolla and the beach at La Jolla Shores or Torrey Pines
- Visit downtown (Gaslamp and Seaport Village)

Of course I am assuming that a week trip means 7 days.

4 days in San Diego and 3 in L.A. -- there's more, I think to do in San Diego with a four year old than in L.A.

I will make the same suggestion I tell everyone, it may or may not apply to you.

When in CA for more than a few days, find the nearest store (or even drug store), and buy the cheapest (foam) ice cooler you can get, some are around $4-5, (Wal-Mart) or then find a grocery store, and stock up on bottled water or your favorite soft drink, buy it by the 12-pack or case.
If you have to stop and buy individual drink items, I have seen a single small bottle of water go for $3 - $3.50 - EACH. And cans of pop go for $1.50. Amusement parks are also just as pricey, some let you bring in water, some don't.

At the end of your trip, see if you can find someone arriving at your motel as you are checking out, and give them the cooler, or, just throw it out.

Regardless of what you do with the cooler in the end, you will have saved a ton of money on your week-long trip.

I agree with surfergirl. The Getty Museum is great but not for a 4 year old. In San Diego you have the Zoo, Sea World, Legoland and the beaches.
While Newport and Laguna are some of my favorite places, I don't think I would want to pack and unpack that many times especially with a child.

Thanks everyone for all your advice...