Puerto Rico?

I'm escaping to Puerto Rico next weekend, returning on New Year's day. Anyone reading this have any suggestions on how best to spend three full days and four nights in a tropical paradise, alone, knowing nobody there, knowing no Spanish (not even enough to get into trouble!), with a rental car and a small pile of camera gear?

My only firm goal is to watch the sun come up somewhere awesome on New Year's Day. I'd like to spend time in the mountains, hike to some awesome waterfalls, and hopefully hit Vieques for the Bioluminescent splendor, but that may be problematic due to ferry schedules.

Or I can just completely wing it. Which is what I'll probably end up doing...