In 2014, I painted signs on empty lots and walls of a torn down building that requested passers-by not to litter, not to urinate around the area and ultimately, not to wear a frown. These reminders may be a bit tactless, and a tad bit violating, but I believe that when you say something nicely, people will be more calm and receptive to you.
Here’s an artful take on everyday Filipino street signs.