Posted this in the Las Vegas forum last month:
Took a couple hours off this afternoon to check out the action. The Rio isn't publicizing the event at all - you wouldn't even know it was taking place unless you drove around back and saw the track and all the transporters and tents set up.
The organizers made a pretty good guess on the size of the crowd. There were three grandstands set up, and they were all just about full when the first heat race of the Superpro class took place late in the afternoon. Tickets are $15 per day. If you go, bring earplugs, and don't spend too long downwind from a running kart - that fuel they burn is really nasty stuff.
http://img257.imageshack.us/img257/7149/riod.jpg (broken link)
A few more big names are in the event - 2004 Indy 500 winner Buddy Rice, and 2005 Indy 500 winner Dan Wheldon. They aren't racing in the Superpro event against Michael Schumacher and the other F1 hot shoes though.
2005 Indy 500 winner Dan Wheldon:
Michael Schumacher's ride for this weekend:
http://img682.imageshack.us/img682/733/schumikart.jpg (broken link)
Schumi working on his kart - I think that's a tiny video camera he's attaching to the radiator. Several competitors had mini video cameras mounted on their karts or on their helmets - probably for a DVD of the event.
You could pay $300 for a ticket to a Grand Prix and not get this close to Michael Schumacher:
Schumi by himself:
Schumi drove from 27th to 12th place and then got stuck behind current IndyCar driver Raphael Matos:
http://img257.imageshack.us/img257/9863/schumimatos.jpg (broken link)
Some action from one of the other classes earlier in the day:
http://img44.imageshack.us/img44/8769/kartrace.jpg (broken link)