How about: "Will pedal for sex?" Not sure which person, based upon the posts here, would be a more likely candidate to wear it.... I do like the notion of "I'm not pedalling... then I'm not steering". I think that puts the whole thing into good perspective.
Stoker Kay used to have a bright yellow T-shirt years ago with a huge black arrow pointing to the left and reading: "Please change lanes"
Surprisingly, it got quite a few smiles and slight beeps on the horn.