Long ago when I lived in SF, the pre-check lines in international were hit or miss as to whether they were open. If the are not, going over to T3 to clear is quite easy.

I'm curious to know if SFO has been hit by the TSA problems present at other airports, since SFO is run by private security. It's now over 2 hours to clear at ORD, and pre-check is getting longer by the day.