General note:

Las Vegas has become one of the largest Seminar & Convention destinations in the USA.

If you want to check if your Hotel has a congress/seminar, Pop star, diva or whatever meeting at the time of your planned visit, than visit the convention calendar of:

Las Vegas Convention Authority.

There you find quick result on Conventions, amount of Attendees per convention, and preferred Hotel.

More useful links:

MGM Grand (weekly updated)

Cheap hotels in Las Vegas (hotels below 30 $ midweek)