We got on in Old Town, and it’s a hop on/hop off tour with stops at the Embarcadero, Seaport Village, Coronado Island, Gaslamp, and Balboa Park, and others. It was enjoyable and the drivers/tour guides are great. One caveat is, there’s generally lots of walking if you get off the bus to see the local attractions (and it’s a 2-hour roundtrip but if getting off at say, two stops and exploring you need to allow more like 4+ hours). Also, it’s not air conditioned, and it was a bit uncomfortable on the 85 degree day that we went. And it can be a rough ride since the suspension is pretty stiff. Currently, they require passengers to wear a face mask.