It's walkable but only a few areas are pedestrian friendly. The places that people think of as traditionally "Boston" (Fenway, Back Bay, South End, Chinatown, DTX etc) are pedestrian friendly. The rest of it is not and there's a lot of land and people in those areas. How familiar are you with the rest of Boston? Walk past Mass Ave. sometime into Roxbury or head out to Roslindale or Mattapan and see how pedestrian friendly it is for yourself...