Get a magnetic sheet and put the sticker on it. Just walk behind your car and take it off when you park.
I get plenty of #1 driver signs in Austin when I have my No BO sign on my pickup. Thumbs up when I get closer to home.
I would LOVE to see an enterprising tv crew set up a car with McCain/Palin bumper stickers then use a hidden camera to see who does what to the car! I'd be willing to bet on the outcome. It would also be interesting to see them plan a car with Obama/Biden stickers in a conservative part of town. I'd bet even money it could sit there for a week and no one would touch it.
Of course I could be wrong on both counts!