It's open to anyone, any time. But it's still helpful ahead of time to register even if you're Bronco-less because it helps us plan ahead. Of course, by yesterday all planning was etched in stone and so further registration wouldn't be as helpful.
Pre-registered people usually get a goody bag when they arrive too.
But glad you were thinking ahead. Hope you made it out and had a good time even without a Bronco yet.
You weren't by any chance one of the folks that purchased one of the Broncos that were for sale there were you? If so, that would qualify as a pretty cool update to this thread.
Paul