Rush at the University of Kentucky is in the fall, the week before classes begin. I think you can register at any time for next fall's rush at the Greek affairs office in Patterson Office Tower, but I think some sororities are currently doing COB (continuous open bidding) so you may want to look into that as well. However, Chi Omega is likely not one of the groups doing COB, so if you are interested in possibly joining that sorority you will have to wait until formal rush. But like the above post said, keep an open mind and you might be surprised--I was a legacy to Chi Omega, in fact, and going into rush that's the sorority I thought I was going to join, but I obviously changed my mind!
Good luck!