If you are staying only 2 nights and have never been before, I doubt you will need (or want) to leave Universal property. There is transportation (via boat, walk, or shuttle) between the parks and the other hotels. You ARE allowed to hotel hop, and both PBH and HRH have great waterslides and pools that are worth checking out.
Be aware, however, that there is nothing really within walking distance offsite. You "could" walk to some of the restaurants / attractions on the north end of International Dr. (and take the I-Ride shuttle from there), however I doubt you would have the free time to do this, and it's a somewhat risky walk since Universal Orlando is basically surrounded by busy roads and the interstate.