Sam says to Valerie: "Maybe we could go up to the Cape for the weekend." The reference is obviously to Cape Cod and, "the Cape" is quite definitely south of Boston. So, anyone based in (and familiar with) Boston would never say "up to the Cape" . . . the operative word would be "down" to the Cape.
When John Allen Hill climbs the stairs at the very end of the story, he can be seen turning left when he reaches the top. This is inconsistent with the layout of the building that Cheers and Melvilles are located in. The wall at the back of the bar is an exterior wall, so he should turn right to enter the restaurant above.