Some will never heed signs it is true but the better the signs are the fewer hardliners there will be, and there IS room to improve the signs.
One thing the signs could do is show a few images from about 1 minute 35 seconds in this video http://www.youtube.com/watch?v=Aszkz_vifUo which amounts to a close-up of the damage done by the "new" path. Outrageous really, and that was in Summer. Not many people wouldn't "get it" that they shouldn't add to that.