People would be bitching if it was done in Vegas during March Madness, well the cheap people would. There is really no time of the year its more expensive outside of New Years and Superbowl. Even cheap places try to charge over $200 on weekend nights. A buddy of mine tried to come in last year during the Tourney and decided to come one week after it. The first weekend the Flamingo, not exactly high priced place, wanted $229/night. The next weekend it was down to $199. Final Four and it was up to $259. The August party was a good time for cheap rates, just don't expect to get a good group deal when people actually have something to come for. If you are going to hold it in Vegas I suggest during the World Series of Poker. It makes for a good gambling atmosphere and late April/early May aren't particularly crowded or expensive around Vegas, and the weather is in the 80s and low 90s so most people will love that.
I second the notion, lets all go to New Orleans. Casinos, lots of bars/parties, and bare breasts for all the boys in the Rubber Room