Well, here there is no problem with putting them on the mailbox. Been doing it many years and have been told by the postal service that it is no problem.
Everyone on this site don't live in the big city. In a rural area door to door sales is still pretty much acceptable. Where I live people will stop by ranches looking to work as a hand. It's perfectly acceptable. I have one area that I work that is about ten miles up the road from me. They have pretty much begged me to come up there and work. They have run two full column, front page stories on my service to try to get me up there to work. No one wants to go out that far and they charge an arm and a leg when they do. Just because you have worked the same city block your whole life don't mean that the rest of the country is that way.