Food:
Hit up the Kogi Truck, Korean bbq, King Taco, little Ethiopia. Some of the best food will be in areas that don't look nice.
The beaches to hit up are Malibu and Manhattan Beach. For the sightseeing, go to Venice and Santa Monica, but don't go into the water, just go for the surrounding area when you go to Venice and Santa Monica.
Don't waste your time in Hollywood or Downtown LA. Both of those places are overrated. Perch is the better rooftop bar in Los Angeles.
Hikes: Hollywood sign is decent, but don't get your hopes up. Hiking Malibu is what you should do, better amazing look for the pacific ocean. The Pacific ocean is cold so don't go in the water.
Bars are only open outside, so just an FYI.