I just spent Saturday there again with the Autosports track day and we all received the same lecture as we did at the Speed Off the Street day, no-one, including spectators, drivers, pit crew etc are allowed near the pit wall. I had a pit crew member with a pit sign and they wouldn't allow him on the wall to hold the sign out for me to come in - They have painted a thick white line on the shed side of pit lane and noone is allowed to cross it... with one exception, you can set up your lap timing beacon near the wall and immediately leave. To quote them "new owners, new rules".
Surely they won't do that for the really big races, pit crew would have to be able to hold their signs up, wouldn't they?