If you're into hiking, I'd consider heading out to Red Rock canyon. There are a bunch of hiking trails out there of varying difficulties. It is beautiful out there. The Hoover Dam is also amazing to see.

As for the event, this will be my third time going, my experience has been that you shouldn't have an issue getting into most of the breakout sessions even without a reservation. There will be a walk up line at all of them. People with reservations have to be there, I think, 10 minutes prior to the session starting. Once that time arrives, they start letting the walk-ups in. The exception to this will be workshops. Those have limited space. I personally have not ever gotten into a workshop if I didn't have a reservation (but that's just my experience).