Al fresco sex is tricky to come by in any big city. There simply aren't enough secluded spaces to get it on without being carried off by the cops. But San Francisco is blessed with one of the largest urban parks in the country, where there is no shortage of sublime spots for lovebirds to enjoy a quickie in between catching a show at the de Young Museum and riding on the carousel. For romantics, the area behind the Conservatory of Flowers provides floral bowers for sweet-scented clinches. Scottish history fans, meanwhile, can enjoy a highland fling in the long afternoon shadows behind Robert Burns' statue on John F. Kennedy Drive. For those among us who like a smooth, soft surface, nothing beats the bowling green's manicured lawn at midnight. And, of course, the windmills are well known among the gay community as the place to go for a casual blow. A couple of general words of advice: No matter how horny you feel, do not attempt to have sex in the buffalo paddock. And bring your own condoms.