This is located at the J.W. Marriott when you go to Rampart Casino. I also would caution that this is a business desk within the J.W. and if you're returning a car, it's actually a difficult situation since it's not marked well.
What you have to do is turn into the valet parking only lot, and at the back is a Hertz 1 and Hertz 2 tag. You have to park your rental there to return it and also remember to memorize or jot down your mileage.
Then you head into J.W. and go talk to the guy that staffs the desk. He's actually very nice (I didn't catch his name) and totally hooked me up with the quoted price even though the people that booked me didn't have me returning the car in the right state (for some reason, it was showing as some CA Hertz place). Same rate.
The one-star off is for lack of signage that could make everything a little easier to deal with. I think I spoke to three different valets that day and they were all really nice in trying to point me in the right direction but it'd be a lot easier if you could just follow the signs to return.