If an 3G lite connection would work, you can get Verizon Wireless from many, if not most, of the areas from the west side of Penobscot Bay on west and south.

If you really need more speed, then you'll need something more than many casual desks at a marina's business center. What location did you have in mind to work from-- or are you roaming? Would you keep you work location a "base"?