Yes. But you must still check in at the 2nd floor desk. They will not let you go up if there is no room for you there. The closer you get to fireworks time, I think the odds increase that you may not be allowed up.
TDC Nala is right--if there is no room (and the bar isn't all that big) they won't let you up.
Best chances are very early, or after fireworks are over.