I like the idea, but I have a few complaints. For best results, use correct spelling. Also, refrain from adding the depiction of genitalia - that's where the focus ends up, instead of the Journey classic. And perhaps you might have thought of something different? This very idea was carried off much better four years ago, right around the corner of my house. Now, if this budding artist had gone with the words "HAMMER TIME!" at the bottom of this octagon, I would have a more favorable view.
Here's an example of how to do it right... I entered a stall to do my business, came upon the picture and caption in blue, and added what you see in black:
I was fortunate to have both the black Sharpie and my camera on me on that day in 2009; the police and/or public works were quick to paint over this.