Jon is right about illegal use of mailboxes. No notes, flyers or literature can be left in or attached to mailboxes unless proper postage is used.
My preferences are in line with what Bob stated. A week after parking my trailer at my son's house someone knocked on the door while their toddler was napping to ask if i wanted to sell it. They got a rude send off from the in-law who was babysitting. A postcard or letter would have made it to me and I would be glad to direct them to this site.
My experience when I owned a burro
was that people who just stopped by didn't realize the value and expected to pay what they would for a tent trailer of that vintage!
As another personal preference, I am always polite to those who disturb me between 9am and 5pm, as I often knock on doors in my community volunteer work. However, when I camp I look for privacy and seclusion. My dog is very suspicious, and in our 13 yrs together I have not been able to dissuade her, so I do not appreciate being disturbed on the road. I won't be rude but I will be terse in those situations. (Of course, some people seem to equate terse with rude. Oh well!)