The best place to people-watch while sitting inside has to be the Wynn, that casino which all kinds walk through to, well, walk through! You can't blame the throngs of passers-by who want to see the classiest, most expensive joint on the north side of the Strip; and if you buy a $15 Sinatra Smash cocktail at Parasol Up, you too can spend a good half hour seeing the world walk by you, amazed at the place.
The rooms are amazing too; automated lights, blinds; the bathroom would be a $2000/mo. apartment in NYC. It's an amazing place.