Hi Mark, with that many days you can see the whole island plus Vieques and Culebra! PM me and I can send you some info on the main island and our little islands!
You can drive around the whole island and spend the night a couple places. I suggest Rincon for an overnight and Ponce. And of course Old San Juan. Rainforest and the Caves at Camuy, ziplining... so much to do!! <img src="http://www.traveltalkonline.com/forums/images/graemlins/Joy.gif" alt="" />