Alright, so let's get started :)
Could be done on a Saturday in a commuter heavy part of the city. We can use this site, ActiveTrans, Facebook and Twitter to get the word out.
may i recommend doing such a thing during afternoon rush hour on a nice day? (a weekend one as well tho). i know it might be difficult to get some volunteers during rush hour, but we can try? i agree that polish triangle would be great...or any spot along milwaukee, really. i dont really know the other big bike commuter avenues.
Tell us more about the Green City Market.
I would also be willing to wear a bikini and wave a sign, ha ha ha.