There are three major international airports that serve the Bay Area: San Francisco International Airport (SFO) as well as Oakland International Airport (OAK) and San Jose International Airport (SJC). There are many direct flights from major US cities to these airports.
The cheapest way to get from OAK or SFO to Berkeley is via BART. It will take between 30-45 min from OAK and about an hour from SFO. Downtown Berkeley is the BART stop closest to the lab and there is a shuttle (the Blue shuttle) that runs about every 15 minutes from the BART stop to the lab. The shuttle is free, but you need to show the shuttle pass that you will be sent just before the workshop.
Training venue:
The training will happen in building 59, and you need to get off at build 65 shuttle stop.
Guest House:
Let the driver know. They will show the correct stop.
You can see the map is here:
https://indico.cern.ch/event/1264566/images/42952-unnamed.png