Yes, you have the cancellation policy correct. You can try Priceline and get a cheaper price, but most of the USE/USW hotels are not that far apart, with the exception of the Nob Hill properties, so you are pretty much in the same location. I myself prefer the Fingancial District/Embarcadero area because of the Omni, which is my hotel of choice. I would accept any of the 4* hotels in the FD/E over some in the Union Square area. The Embarcadero area is not as busy as the Union Square area pedestrian wise, and the incidence of homelessness is less. Transportation is easy...a cable car goes back and forth on California Street, and the F-line trolley goes back and forth on Market to Fishermans Wharf. The Muni subway can get you to the outlying parts of the city easy enough, and a 7 day pass for unlimited use is $26. The ideal hotel transportation wise would be the Hyatt Embarcadero. That's all for now, you still have plenty of time.