Down Cape

Close, but Cape Codders refer to it as the Lower Cape, for the northern part, mid-cape for Hyannis/Yarmouth, and Upper Cape for Bourne/Falmouth.

you go down the cape but when going into Boston you say I'm heading intown

I grew up in Sandwich, where everything except Bourne, Mashpee and Falmouth is down Cape. It's a direction, not a place.Most of the directional bits seem to be simply eliding a preposition: "going down [to] the Cape," or [to the] cella, or whereva, or "in[to] Town."