Replying to Getting a metal street sign off of a brick wall?

There's a sign in my town that i would like to borrow... but i'm not sure how to go about taking it down. It's nailed in with what i think are flatheads, but there are washers between the head and the sign. I'm hoping i can just pry the nails out with a crowbar, or if that doesnt work, try to break them with a hammer since they're rusted. Anyone have any experience with this and know of a better way to go about doing it?