There should be plenty of dedicated public places, walls or areas where people could post up advertisements, lost pet notifications, yard sale signs, or other signs or notices. This way telephone poles, light poles, and many other places would be free from staples, tape, torn paper, awkwardly mounted fluttering signs, and all other kinds of things that make many places look bad. Dedicated places could be designated within certain areas of supermarkets, gas stations, post offices, schools, public parks, etc.
All these areas could be swept clean on the same day once a month or once every two months by government workers so that there is not a buildup of outdated material. These clean up schedules would be posted at each location so that everyone who advertises there would know that their material will be removed on that date unless they come before then and want to remove it themselves to save it. Posting up signs in these areas should be free to the public. However, maybe next to these open displays there could also be glass or Plexiglas display cases where people could, maybe for a fee or special arrangement with the proper authorities, have their signs or messages protected from the weather and vandalism and/or arrange to have them left there through a certain number of the periodic one or two month purging periods.