Street art in China seems non-existent to poor. Much of the graffiti I saw was rather dull, at most a single word or hastily made design on a vendor's roll-up door. Part of the problem is that there aren't a lot of "blank canvases" in China, almost every surface is covered with commercial art already.
There is also what I would call “official” street art. Certain places have murals in the street art style, sometimes for advertising or propaganda purposes:
I did see one place where students had been allowed to create murals to decorate a wall around a basketball court:
Stickers here almost universally contain a series of numbers. I'm assuming they are advertisements for prostitutes, but I can't say for sure.
As to the prostitutes--when checking out of my hotel in Zhongshan (a lovely place where the toilet is in the shower) a well dressed woman was standing at the counter:
I took her for another guest, or maybe the manager. She seemed rather brash (loud) and I thought she might be drunk. She offered me cigarettes, something to drink (a boxed drink) and felt the material of my shirt. At this point, my limited vocabulary in Chinese was to my benefit, because in trying to get across what she wanted she showed me her license (a plastic card with her picture on it) and a bill from the hotel (they rent rooms by the hour on the first floor called “spread the grass” rooms).
In Xiamen the prostitutes have a little more class. They team up and hire meek men to hand out clumps of “business cards” showing them in various states of undress, along with their phone numbers. “Please call” the men say in English as they hand out the cards.