In an ideal world, I'd have left work at around 3:30 or 4:00 in order to avoid the traffic mess. But in reality, I got stuck at work until 7:00.
According to NextBus, F-Markets were not leaving Castro and Market, and few were leaving Fisherman's Wharf. So I walked to Embarcardero Station from my office (about a mile).
When I got out at Castro Street, there were scads of security in yellow vests to ensure that people didn't hang out on the platform when they got off the trains. There were barriers to define where you could and could not walk. No one leaving Castro Station was permitted to leave the station on the south side of the street -- everyone was directed to the north exit, where virtually everyone crossed to the south side, several in costume, and many more carrying cameras.
When I got to the surface, there were at minimum 20 police officers on bicycles preparing to ride down Castro. The streets were lined with police barriers (and police on foot) to ensure that people didn't try to jump into the street.
I tried to stop by Castro Cheesery to get some coffee (because I'm completely out), but they had closed early. So I continued toward 18th in order to go home.
But there was something going on in the intersection of Castro and 18th. There seemed to be a huge horde of people on bicycles (some in costume, some in street clothes, and a few in neither) swarming the intersection and blocking traffic. An horde of police on bicycles were pushing through them to force them to disperse. The intersection was so crowded that pedestrians couldn't even cross the street. I waited for about two minutes, and the blockage started to disperse. Eventually, I made it around the corner and got home.
I'll be interested to see if the police succeed in keeping people out of the street..
[UPDATE: Channel 2 just reported that (a) the cyclists were pretty much just that -- a bunch of bicyclists who showed up and started circling in the intersection; and (b) the police have pretty much succeeded in keeping people out of the street. Meanwhile, a helicopter has been circling overhead for the last half hour or hour. It makes me feel like I'm in Los Angeles....]