Little or no chance to get in the pits for a GP,I'm afraid.I read that the Spanish organisers have introduced swipe card pit passes to stop folks passing them on.
I once won pit passes in a Fast Bikes competition.I met all the superstars at the time,Shwantz,Rainey,Doohan,Cadalora,etc.
It was a bit overrated really.

I had pit passes to last years WSB at mangy corpse, and really enjoyed myself. Most of the riders were happy to stop and chat (except Hodgeson after he fell off!).

Might be a bit different at GP level though.