The OP asked about the conditions at the Stadium. The below web address is the actual conditions as posted on bowl.com.

http://www.bowl.com/downloads/pdf/tournaments/OpenChamps/2007LaneConditions.pdf

Other posters have advised to take several different balls. This is a must!!! However, you should also know that if you travel with 3 balls in a bowling bag you WILL have problems coming home from Reno. Most airlines will accept a 3-ball bag as a piece of checked luggage. Normally you can get on the airplane at home without question. For some reason baggage handlers in Reno have protested this policy and charge for overweight/oversize parcels. I was witness to this in 2004 the last time Nationals were in Reno. A traveler was arguing with an airport supervisor about the airlines acceptance of the 3-ball bag as a normal piece of checked luggage. It got to the point that he was in jeopardy of not going home. It ultimately cost him extra to check his bowling bag. The National Tournament has a service called Bowling Ball Express (BBE). Using it, one can ship their equipment to the venue and the BBE people will accept shipment and have everything ready for you when you get there. When finished bowling you use BBE to ship them home again. They won't accept bowling bags, so just use your bag as a suitcase. Fill it with clothes and take it with you on the air plane.

Have fun
Mike

When I use a spare ball for my 10 pins, I use it all of the time. Going back and forth messes me up more than the lane conditions could ever do. That being said, neither way has really worked for me at Nationals :-)