I prefer the SFOAirporter service (lots of full-size buses and some hotel-shuttle-type vans). Last time I rode them (9/10), One-way was $12 and they run every 20 minutes or so each way from about 4:30 am til midnight. No reservation needed. Clean, reliable, professional, and fairly cheap. They can be found at: www.sfoairporter.com
They've never disappointed me, but nothing in life is guaranteed. Have a safe trip; glad to see that travel continues.