<p>Hey stly 
511.org is your friend! It says you can take SamTrans KX Line for $4.50 from SFO to the Transbay Terminal, with the following luggage restrictions: “If a passenger can carry the item(s) on his/her lap or store it under or next to him/her on a seat unneeded and not hurt anyone else, and not interfere with others, the item is probably safe to transport.” The final decision will be made by the bus operator, who is responsible for the safe transport of everyone on the vehicle. </p>
<p>You’ll probably have to work out the details yourself on the website, but the parameters you’ll probably want are Fewest Transfers (saves money), Adult Fare (because you’re old), and Maximum Walking 1 Mile (again, saves money). Hope this helped!</p>