antagonistic guerilla art idea:

set up chain link fencing or pedestrian barricades into small pens in public areas. like i'm talking 25 sq ft, like a little box. hang a sign that says "Free Speech Area" on it with maybe a ticker or decal of the local institutional authority (county/municipal government, state, university, etc). set them up over night and in areas with lots of foot traffic, but not blocking or even remotely hintering people. like totally tucked into a corner, but completely visible.

it would not be cheap, because that stuff can be pricey to lose and they will take it once somebody with enough juice realizes its fake... but it could last in place for a while and i think most people looking at something like that resent the shit out of it.