Its been a long time, (like 40 years ago) but I was in the Navy aboard a ship for about 4 months at Boston's south annex. We got around on the subway/rail system (now the MBTA). Most of the stations had parking lots for folks that commuted. Crowe may be able to get you headed in the right direction. My memories from back then are foggy, but I remember that parking downtown was impossible. I don't imagine that its gotten any better. You may be able to commute from the RV park to downtown and back on the MBTA. If you're staying in a downtown hotel for the conference, you only have to make the trip once in each direction. Driving in downtown Boston isn't for rookies.