ashok r.
Yelp
The other reviews are pretty comprehensive, so I'll just add a few points:
Court condition - probably resurfaced in the late 1990's, so they are pretty fast, but are fine overall, and the paint is consistent (no asphalt showing through).
3-ball rule - I usually have 3-6 tennis balls, and have never had a problem. The only people who are allowed to give lessons (and use the big baskets) are the pros associated with the park, and the money they generate is used largely for court maintenance.
Pick-up games - You can usually show up and find some people to rally. Walk over to where the wall is (northeast of the courts), or just look around for any group of 3 people hitting.
Court-time - It is great to have a facility with 21 courts, as you can usually just show up and get a court (without an advance reservation). If the courts aren't too busy (weekdays), they usually don't require people to pay the $5 fee (90 minutes). If things are busy (weekends), then the reservation/fee policy is more often enforced. If you aren't sure what that day's policy is, walk over to the "clubhouse," which is at the southwest part of the court area, and ask!
Court spacing - I don't have an issue with the courts being spaced too close.
Wind - sometimes an issue, but that's life in the city, no?
I like playing here because (i) you get to see so many other bay area people enjoying tennis in one (attractive, tree-filled) setting, (ii) parking is easy, and (iii) court-time is reasonably easy to obtain.
So get out there and play some more tennis!