Take a vacation, continue working or volunteering at a place you enjoy, spend time with your friends and family. I had the same question last year before I started, and my initial knee-jerk response was to start studying frantically since we had a test the first week. In hindsight, my studying gave me only a minor edge, and by the 3rd or 4th week of classes I was on the same level as my classmates.
By all means, if you want to study, go for it. Don't go overboard and forget to enjoy the abundance of free-time that you have now because you'll definitely have less of it later. PT school so far has been tough yet as rewarding and exciting as I was hoping it would be. However, it will require adjusting to a new lifestyle, so go on and have fun before it starts!