The El Yunque rainforest is a great FREE getaway.  The tours from area hotels range from $40-$50, but it is totally FREE to get in. Rent a small car (using Hotwire or Priceline, never at the hotel).  Drive up to the El Yunque rainforest, which was only a 45 minute drive. There is a small $1.50 toll on the highway.    If you would like the tour guide experience without the large cost, stop at the visitor center and pay $3.00 for a short movie and handouts with information on the area to conduct a self guided tour. 

The Bacardi Factory Tour is free as well.  Transportation to the island is $.50 and the cab ride to the factory itself is $3.00 per person.  Bacardi gives you two free drinks and a guided tour of the plant for FREE.