Peixotto Playground and tennis courts are on the north east side of Corona Heights Park. Available there are two tennis courts that are pretty well-maintained and a great playground with a big slide and climbing structure, swings, and a sand pit! There is grass to run around on or have a picnic, and plenty of paths that lead to other parts of Corona Heights Park.
Peixotto Playground is owned by the San Francisco Recreation and Park Department.
Additional Info
On weekends, advanced players congregate at the tennis courts around 9am-1pm. You may be able to join a pick up game.
Muni access:
24-Divisidero -- 15th St. and Castro. Walk west (it's a bit uphill), around the slight corner to Beaver. Go left on Beaver and look for a narrow walkway that leads to the playground.