All this pool talk and it's going to be January.... I doubt the hotties are going to be at the pool.... unless it's some freak hot snap....just saying.
Hard Rock is way too far away from the Rio... so is Luxor, Manadalay bay, NyNy, MGM, Excalibur, etc...
I personally love the MGM grand (you really can't beat that horse racing game) but it's too far from Rio too. I'll probably try to stay at the Bellagio, Mirage, Treasure Island or Rio. All depending on how things go in the next few months.
Also, I wouldn't book this soon. Just my thoughts from being there quite a few times. I've found you can get some good deals a bit closer to the dates. When you book (go through the hotel as it's usually cheaper and can include promos) check on the 'specials' on each website as you can normally get some sort of 'free spa pass' or something like that. Also, ask for a strip view when you check in ( the non-strip rooms suck) and if they won't give it to you slip them a $20.
I may have been to Vegas too many times because this could be my most useful post on WF.