If you're out on the Charles, lots of the boats you see will be from Community Boating (near the Hatch band shell, where the Pops perform, on shore). Community's a great program, if you're interested. it's made sailing available to many who wouldn't have had a chance otherwise.
So out there, you will need to know who's on port or starboard.
I've been away from New England almost 30 years, but don't think any of the above has changed.