The Santa Monica Farmers Market on Wednesday mornings at Arizona and 2nd Street is widely considered one of the best in California. Chefs from restaurants across Los Angeles come here to shop, which is generally a reliable signal of quality. The produce is seasonal and genuinely local — stone fruits in summer, citrus in winter, strawberries seemingly always — alongside vendors selling olives, cheese, herbs, nuts, and prepared food.
The Saturday market at the same location is larger and more accessible for visitors (the Wednesday market opens at 8:30am, the Saturday at 8am), with a wider range of craft vendors alongside the produce. Both markets are outdoors and walkable from the Metro station and the pier area. If you want to understand what Southern California agriculture actually produces, this is the place to see it.