The scene with the mass hypnosis, supposedly in Cincinnati, is clearly in the main lobby of the Dorothy Chandler Pavilion in Los Angeles. The banner with Placido Domingo's name is even clearly seen hanging outside.
While Buck and Troy are being driven around Cincinnati, you can see palm trees out the back and side windows of the limo.
Alan asks a host to show "Troy and I" around (instead of "Troy and me") near the beginning of the movie.