I've been to the SX finals in Vegas. Plan on making a day of it as there are other things going on in the pits to enjoy between watching practices and the actual race like tire changing contests, racing RC cars, things on display, etc. Pits are pretty much open to the public. The race rigs are all lined up and have canopies with a little fenced off area in front of them. You can watch the mechanics clean and prep all the bikes and when the racers have some free time they will sit by the edge and sign posters for fans. We got there right when practice started and watched that before going into the pits. Seems most of the racers were in work mode then so it might be easier to get an autograph or meet them earlier in the day.