Lawrence Berkeley National Lab is easily accessible by public transportation from SFO and OAK international airports. Attendees from foreign countries should check their US entry requirements at travel.state.gov/visa/temp/types/types_1265.html (there are new requirements even for the visa waiver program). Contact the email@example.com if you have questions about your entry requirements.
Winter in the SF bay area is mild, but wet. Steady rain for 3 days non-stop is a possibility. On the other hand, when it is not raining it will be sunny and mild.
Useful local information cane be found at www.lbl.gov/visitor-info.html.
The workshop will be in Perseverance Hall inside the cafeteria building. The picture below indicates how to get there. The shuttle bus routes can be found here: http://www.lbl.gov/Workplace/Facilities/Support/Busses/all_routes.html. From the Shattuck hotel take the blue route bus at the stop on Shattuck street (near the corner with Addison).