I've had the opportunity to talk with several experienced pilots on the hanggliding.org forum, and asked about plyometric exercises to prepare for my training. The consensus among them was to stick with basic walking exercises, and to try not to overprepare. One interesting point was that human habit normally causes a person to slow down when running down a hill so that a person will not loose balance and fall over, while this is a bad habit in hang gliding.
I am going to stick with my regular workout routine.
Meanwhile, I am reading Dennis Pagen's Hang Gliding Training Mannual and observing the many different hang gliding videos on youtube. I make it a point to observe videos of good flights, as well as videos of crashes and bad landings.