I'm not sure. I took an Uber from Megabus landing station to SFO. Yes it took much cost. I think you can take a Lyft or Uber pool to nearest BART station to go to SFO.
The Greyhound Station is not far from CalTrain which offers service to the Millbrae transportation hub. When you reach Millbrae transfer to BART which runs directly into the airport. You can also catch BART from several points in downtown San Francisco. Depending upon weather and how much luggage you have, you may want to take a cab or Uber to the nearest BART station, but its not too far to walk. Just ask someone to point you toward Market Street.
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