great way to explore different areas of san francisco at your own pace. very convenient locations to get on and off of.
Great guides on the hop on hop off bus...enjoyed the service was very friendly.
2 days on the big bus is too much. It is not a good way to hop on and of to enjoy different sites in San Fran. It is a good way to get an overview of the city and then return to points of interest by walking or Uber. So I would do a one day big bus and alcatraz combo