This is a great idea derived from the hobo signs or actually it goes way back see: Gaunerzinken #800080 size=1>(English version). Agree on signs that show where wireless access points are.
Have to get my wireless router going again and a sign outside my home. Last week I put a bench in front of it for tired people walking by to rest, and of course for me to sit and enjoy the afternoon sun. It worked already, saw some people sitting there, which made my day. Can