Use swimmersguide.com and you will see both of these...I have gone to the muni pool downtown many times. Always set short course when I have been there but going mid day there are a ton of lanes and it has never been busy. Locker rooms aren’t flashy but they are fine; the staff is nice and it’s cheap. The athletic center at UNLV is very highly rated and I’m planning that the next time I go; it’s just a bit more expensive and it’s an Uber for me because I never have a car. Lots of other options too if you have transport but those are closest. I would NOT waste $20 on a day pass to a Las Vegas Athletic Club. Hope this is helpful!
http://www.swimmersguide.com