Here in Oakland, our severely mild climate means that pretty much any food-bearing plant will grow outdoors if you give it some space and perhaps some water because drought. You can find many kinds of berries, citrus trees, and other plants growing in parks or public-enough-seeming locations.
If in doubt, ask! Many people with edible plants are sick and tired of having so much fruit all the time and would gladly share their bountiful harvest with some polite wandering vagabond.
Forage Oakland is a foraged fruit barter network. They have lots of materials about Oakland fruit, what fruit is in season, wild-food-related events, and more. (Note: I thought that they used to have a fruit map but I can't find it anymore. Any help here would be appreciated.)
There's also a magazine called Edible East Bay. It's kind of fancy.