I'm near New York City, where the police see their role as standing around and collecting overtime, and generally people get arrested only if they make a concerted effort to do so. So, I would suggest carrying small signs that you can print out on your home printer and attach to a piece of cardboard--your arms won't get tired the way they do with a big sign.

And I recommend bringing a Victorian novel. There's a lot of standing around, and you won't finish one of THOSE puppies in a hurry. And if you do get arrested, they work well for reading aloud in detention areas as a substitute for the cozy English fireside.