First of all my caveat: Nancy and I don't go to the Bub's event. But -- I know that in the past Bub's has had an arrangement with one of the casino/lodging facilities to provide a decent room at pretty low cost. Maybe try the Bub's website (there's a link on the home page of landracing.com) to see if said casino is listed.
Other than that -- there's a Motel 6, which isn't all that bad, and a Super 8, a handful of the more-expensive chain motels, four or five casinos (including the lowest cost one, the Red Garter), and a few independents. I don't think there's any one that's THE place where racers congregate other than maybe the one that's in cahoots with Bub.
How far in advance can also be written as "How far in advance will they let us reserve?" That is, for SpeedWeek there's usually an agreement that no reservations will be accepted before the first of the year, or some date around then. For the record -- when that's the case it seems that if you wait even half-a-day on the appointed day to make your call -- the town is already sold out. As I remember this situation has been changed for SpeedWeek '08 -- a change in the date of the event, and a change in some of the policies of the casino/hotels. Do your own due diligence, and we'll see you on the Salt.