I live in Louisville... If you are headed this way, prepare for heat. We're in the upper 90s every day now. Perhaps we'll see a break into the upper 80s early next week, then right back to 95+.
Churchill Downs will probably not be running races during the rally dates. They stop racing during the heat of the summer, and as I recall, the spring meet is just about over. The excellent museum is still open, however, and it is very close to the expo-center which is hosting the rally.
The Louisville Slugger museum is also good, as is Louisville Science Center, the opera house, and the Frasier Arms Museum downtown. For those looking for night life, 4th Street Live downtown is a grand mall that has a number of venues, from Planet Hollywood to adult entertainment (not for me, but its there).
Just out of town, south, is the bourbon highway, where you can take tours of Jim Beam (with samples of the "good stuff" like Woodford Reserve), Maker's Mark, etc. Also of note is Fort Knox, south on Dixie Highway (less than 40 minutes from the fairgrounds) which has the Patton Museum and the gold repository (not much to see there - surprising how small it is!). Our zoo is fun and decent for its size with some interactive animal exhibits (don't expect the San Diego Zoo!).
Plenty of city and high end golf courses, which wind around the park system designed by famed architect Frederick Law Olmsted.
http://www.louisvilleky.gov/Visitors/