I always try to keep my fitness in gear when traveling on biz.
Vegas with all it's sinful temptations of food and drink can ruin it for me so I always try and hit up a casino gym while staying there. The Grand Spa at MGM was a decent little gym with some nice equipment. Very well kept, plenty of cardio, and a good line of machines, dumbells, and some cable equipment. Also on hand are complimentary bottles of water, fruit, and assorted Nature Valley granola bars.
Hours: 6:00am - 7:00pm Monday - Thursday, 6:00am - 8:00pm Friday - Sunday
Overall, nice gym for a casino with plenty of equipment. $10 a day gym only fee is a deal.