They aren't going in there anyway. They don't have to. Protestors asked for a place closer to the convention and that's why they got that crazily secured area.
"At times, there were as many delegates and tourists as protesters at the designated ''free speech zone'' near the FleetCenter, where the four-day event was being held."
"A march by the Bl(A)ck Tea Society, a self-proclaimed anarchist group, and other groups, drew an estimated 200 protesters who wound their way through the city accompanied by about 50 state and city police officers on foot and motorcycles."
"Elsewhere in the city, Buddhists held a silent vigil for peace at the Holocaust Memorial near Faneuil Hall, and rowdy supporters of perennial presidential candidate Lyndon LaRouche began singing loudly on a subway car, mocking the DNC volunteers on board."
"The Bl(A)ck Tea Society's day began with a two-hour rally on the Boston Common, a 50-acre park once used for public hangings."
http://www.boston.com/news/local/massachusetts/articles/2004/07/27/protests_mostly_tame_on_first_day_of_democratic_convention?pg=2