Most hotels restrict pools to guests only and you have ti prove it with room card. At cheaper places with boring pools you might get in - not sure. But any pool you would want to visit is definitely for guests only (and perhaps you have to rent cabanas or lounges or whatever as well in high season).

Some of the hotels have outdoor pools that you can look at from public areas, like the parking garage.

As has been said usually hotels are pretty strict about who they let into the pools and they check room keys.

One nice pool area that you can usually get into without a room key is Flamingo (http://www.vegashotelpools.com/hotel-Flamingo_Hotel__Casino_Las_Vegas-24).

The Flamingo does have a great pool area that all can walk through. The actual pool requires a room key but if you're not swimming you've already seen the best part.
The Bellagio allows anyone to walk out on the back deck/veranda that over looks the pool and garden area.
These are the only 2 I remember but were very nice.
As far as general hotel areas; Lion exhibit at MGM Grand, Paris shops, Bellagio conservatory(flowers and such) Venetian gondolas- indoor and outdoor.

Thanks for that info. It helps a little to figure out how much time I want. I basically wanted to know where you could generally go. Obviously these places want people in addition to hotel guests to frequent the money making areas - casinos, shops, restaurants, etc. but wasn't sure how things were laid out. I've never been to Vegas (obviously) but when I was in Monacco last year they wouldn't even let you into the casinos unless you looked like you were there to gamble - e.g. no "tourists just looking around". It seemed from what I've read Vegas is different.

Yes, Vegas is nothing like Monte Carlo - more like Atlantic city (housedress and slippers are OK as longas you're putting money in the slots).

Monte Carlo cainos are definitely NOT a tourist attraction - but only for gamblers - and to get to the inner rooms they definitely want you to look upscale (and bet a LOT).