-and- still yell/scream during defense, big plays, and things like that. I do it just fine. 🙂 Nothing better than when the entire stadium rises and is making tons of noise.
With that said, I also am against forcing the fan base to do things by having a random fan with a sign in my section. The atmosphere and fans getting loud should come organically and naturally, not from an annoying fan waving a sign in my face.