I can't say San Francisco is walkable the maps are very deceiving. They should all be topographical maps. My suggestion is always use public transportation, cable car, street car, bus or BART it really beats walking. If a hill has to have steps cut into it is too steep.
So I tried to hit all the major "touristy" highlights, Fisherman's Wharf, The Ferry Building, Grace Cathedral, and Alamo Square. Now that I know how to get around I can't wait to go back.