I was in Vegas for a conference in April and stopped by the Hall of Fame with a friend. We had an absolute blast for 3 hours before our flight home. It's a must-stop if you're visiting.
Cab situation is tough at the PHOF because it's pretty close to the airport. You CAN flag cabs in that area (you can't on the strip), but most cabs are driving by with passengers on their way to the airport. Calling is a good idea, but as RobertWinter mentioned, expect to wait 30 minutes or more for someone to show up.
We ended up hailing a super nice lady after about 10 minutes of standing next to the street with our luggage. There was a solo guy who had been wandering the PHOF most of the time we were there and he called a cab at the same time we were trying to flag one down on the street. He ended up hopping in with us. The lady had her taxi light off on a break and was on her way to get ice cream and saw us and stopped, so we lucked out. We bought her the ice cream