Parks are nice. Parks are pretty. Parks are fun to be at. But note that plants in a park usually don't bear fruit. You've got oak trees, maple trees, spruce trees. But no apple trees, typically. Meanwhile, private residences often put up fruit trees. There are apple trees by the side of my house. But the owners typically don't like you plucking that fruit. Pretty much just an accepted thing.
Currently under construction is the Beacon Food Forest, in Seattle's Beacon Hill District, funded through money from a park levy from back in 2008. This is a concept common in tropical regions, but not nearly so much in temperate zones such as, well, most of the United States. Fruit trees- as well as nut trees- will be planted in lieu of the maple/oak/etc. assortment, in not only the more common varieties but also some more uncommon ones, at least for Seattle (for example, pineapples). In addition, berry bushes are to be planted. They also plan to have beehives around, so there's honey available as well. It's originally slated for two acres and the plants will take a bit of time to start bearing fruit, but eventually, if this works out, the plan is to tease it out to seven acres, making it the largest such garden in the United States. Any food they bear is to be free (though garden plots are eventually to be leased out for $10 a year), with people invited to take as needed on the honor system. This of course means some asshole could come along and empty all the trees and bushes of every piece of food in sight, but organizers are hoping that guy doesn't come along; if he does, the solution is basically to plant so much stuff they can't possibly get it all.
Or that he doesn't know how to properly collect honey.
If you happen to live in Seattle, they are looking for volunteers to help plant all this stuff and maintain it once it's built. The people to contact for that are here. If you're not from Seattle, they also take money.