The main outside restaurant-great view of the valley
Another option is near the entrance where there is another , but smaller outdoor bistro.
An outside Bistro at the Getty Museum
Also, if you can downstairs from there, there is a gourmet cafeteria style walk up order area that serves an abundance of different kinds of food. If it is a hot day, being inside will be very relaxing.
Great food in the cafeteria of the Getty Museum
Next-more photos of the grounds and the architecture