The graffiti messages should be in Aurebesh, right?
Maybe a little Aurebesh for the aesthetic, but I think most of the text should be in English. We can’t really focus on the artwork at all (…can we?), so I think we need to go with whatever’s most apparent and accessible to a casual viewer. If people see a bunch of hieroglyphs, it won’t convey anything; if people see messages they can actually read, the intent will be clear.
Obviously, the pictures and symbolism will help, but are people going to notice that and understand the significance of it with a quick glance in the background? I don’t think they would. “SKYWALKER LIVES!” That would catch their eye, and make everything that much more apparent.
Besides, Star Wars had a bunch of English before the Special Editions came along, so we’re not breaking lore or anything…https://www.youtube.com/watch?v=uvbrVFP_f0w&t=3m28s