There are two main events on Biscayne Bay during Columbus Day weekend. They are the regatta that Jack referenced & also some raft up parties over towards Stiltsville or off of Eliot Key. The Regatta is the more civilized event & is self regulating. It is also USCG sanctioned, with a permit. The raft ups used to get wildly out of control & are now heavily monitored by law enforcement, with special anchorage restrictions, speed limits, etc. for the weekend. The last time I did CDR, about 10% of the racers also went over to the raft ups at night. They generally didn't finish well in the following day's races. If you want to get a flavor for what the raft ups were like in the old days, you can poke around You Tube a little. Some of the cleaner video clips may still be up.
The regatta that Jack referenced is the event that I was recommending. It is probably too late to register a new boat now, but you can probably get on a current boat as crew if you hang around the bar at CGSC & let it be known that you are looking for a seat.
I find it amusing that the event that is principally sponsored by a major rum producer, is the more well behaved of the two events.