First, let me state the obvious and say that Matt Groening is a comic genius. His "Teachers' Guide to Words That Make Kids Snicker" in the aptly titled School is Hell was the inspiration for this compendium of funny signs around town.
Immature? Yes. Juvenile? Unh-hunh. But the next time you see one of these signs, I bet you'll giggle like a schoolgirl and wonder, "What were they thinking?" I know I did.