Of course, one could go the official route and try to get your municipality to make up official signs to post, put ads on busses, etc. But I'm thinking why not make a bunch of signs yourself, computer printed and copied in color if you have the software/skills/money, laminated against the weather, and put them up yourself? On telephone poles or other signs, facing the wrong way, of course, where the wrong-way cyclists will see them. Backs of signs might be good. Some big type at the top to grab their attention, then smaller type explaining about the law and safety issues, for if they are actually curious enough to stop to read it. Sound good? Ideas for text?
I'm thinking the big text at the top should be "RIDING AGAINST TRAFFIC? DON'T!".
Maybe if local officials see them, they might think it's a good idea and continue it.