No Problem!  You can go hang out by the Pool at the Hotel San Carlos even though you are not a guest at the Hotel!  That's right, every Saturday and Sunday from 1 to 10 PM, the general public is free to come hang out at the Hotel Pool, which I believe is located on the Third Floor.  Anyway, they have a full bar and live DJ style music and it's a real, live, Downtown Phoenix Pool Party!

Hotel website