Looking for options for traveling from Napa to San Francisco with a group of 14 without rental cars?
Thomas has it right! There are a number of companies from which you can rent vans, buses and limos for group travel. A simple Google search should yield some good results. :)
Small plug for the company I work for, Tilt, if you need an easy platform for collecting $ with your friends. We often "tilt" limos, etc. for ourselves and it has worked super well.
Enjoy your trip! :)
The most convenient option with that many people would probably be to bus it to the Vallejo Ferry Terminal and take the ferry into San Francisco (that's probably the most scenic as well). You'll have to check times because I know the Vallejo Ferry doesn't run that late.
Good luck and enjoy your trip!
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I suggest you shuttle (or Uber) from Napa to the Vallejo or Larkspur Ferry and return to the SF Ferry Buildling by boat. Be sure to check the schedule so you don't have a long wait. It is a beautiful ride and no traffic. From the Ferry Terminal you can walk or take muni (sf city bus) to Union Square. I believe the ferry is $7. The ferry is a great, scenic option and special to San Francisco.
The best option would be to rent a luxury van or small bus that can take you there. There are plenty of operators in the area.