My favorite farm around LA is in Moorpark. Although it takes about 45 minutes driving, I always go there in the Spring.
One of my reasons to go to "Underwood Family farms" is that they have a great market and you can buy fruits and vegetables at local, homegrown prices. My recommendation is usually the tomato, onion and asparagus. You won't forget the taste.
My biggest reason to go to this farm is the STRAWBERRY picking. From March to June you can pick your own red and juicy strawberrys. May is the best time to go there. Finding a strawberry is such a cute thing and the taste is totally different if you eat them right away, it is very sweet!
Going to the farm is a perfect spring activity in LA. (because summer time is always too hot!) Spring is the best season to go strawberry picking, watch sunflowers bloom and get the freshest most delicious vegetables.
"Underwood Family Farms"
3370 Sunset Valley Road
Moorpark, CA 93021
45 minutes driving is worth it to visit the farm. The people working at the farm will welcome you there and treat you very nice!