Lots of good restaurants/bars in Santa Monica. Meat on Ocean is where I had the best steak of my life. There's nice beaches and hiking in Malibu (you could go to the Getty villa).

In LA, check out Olvera street. The Last Bookstore if you're a book nerd. There are some good museums, the broad, the getty, the museum of death. Lots of good food options at grand central market. The Griffith observatory at sunset.

In OC, the nicest beaches are in Laguna Beach (Victoria Beach, table rock, crystal cove). Olamendis is a fun Mexican restaurant on the beach at Dana Point and has the best margaritas.