Yes - assuming there are no blackout dates. Your best answer would be to try looking up some dates using points. I tried over June 28 to July 5, 2011, and the June dates were unavailable for using points; July dates were available, but I chose the Resort out of town instead.
Yes you can use the points to stay at the Cosmopolitan in Las Vegas. Its a great hotel and its in the middle of the strip... Service is great, rooms are very nice with modern design, nice size baths and view can be astonishing depending where you get the room. awesome hotel.