Key West is pretty cool, I went there when I was 17. Yes, you can just go hang out. The beaches there are not really sandy beaches, they are rocky. Be sure to have those water shoes or sandals - I love my Nikes. I remember there is a street called Duvall, where everybody just goes to hang out. I think was a market place to go shop for local items like seashells and other stuff made by locals. Somewhere in Key west, not far from Duvall (I think) there was a place like a boardwalk. IT is supposed to be the greatest place to see a sunset. There were street performers - very entertaining. Keep in mind, that was about 10 years ago. Things probably haven't changed that much. But key West was pretty cool.