Ditto what the others said - get a cheap rental car. Easier & less hassle.
Eat at the 'nice' restaurant at the Getty (it's above the cafeteria). It's only $1-2/more than the cafeteria prices, but great views, service, food - and you're not in the busy cafeteria environment.
There are a few eating options at the Getty; I wouldn't bother going off-site.
Enjoy it - and if you get a sunny day, the views are fab (in addition to the art) - Catalina Island to downtown LA. Cheers.
Sharon