Oubliette, I actually thought of doing this once or twice.
Does your condo project have a common area like a cabana? You might rent it for a night and pass the word you're having a seminar on how to talk to JW's when they're at the door. You could give them a few good talking points to bring up and tell them that if the JW's ask where they get their information, they can say that somebody that lives there is an xjw, and runs a class on them.
With a bit of luck, you may be able to get the whole project put on a "don't go here" list.