I've been to Folsom many years in a row. It's a fun event but has become popular with the straight community as well to come and look at the "circus".
It is a one-day event every year on the last Sunday in September from 10-6 PM but events surrounding the event take place all weekend long.

You will find guys letting it all hang out. Every year I've seen a few of guys who attend totally nude - except for shoes. On the street sexual activity has always been more tame than what Southern Decadence use to be like but it does happen. But it certainly happens in the bars that weekend.

In the past 10 years, its only rained one year at Folsom, prior to the event, which shut down all electrial related events (no outdoor music, no dancers in cages over the event). Otherwise it has always been a blast but very crowded.

This weekend they are having the worlds first "Bear Street Fair", the new Harrison St. Fair.