I'll let you guys talk about the panhandling signs, but I'll add to the graffiti...
Some of what I've seen has been artistic license by the tagger and some of it is pseudo-gang related. I say "pseudo" because it isn't very good nor imaginative, more copy cat than anything.
I'm surprised someone hasn't tried to copy or emulate Banksy or Fairly around here. There's a lot of blank space on the Harbor here.
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Remember, remember the Fifth of November, Gunpowder, treason and plot...