Michael, in my opinion a trip to Puerto Rico should a whole separate visit as there's just too much to do in Santo Domingo. DR1's recommendations are great. Do spend time in Old Sto Dgo (the Colonial Zone), this is truly a unique experience. There, you will be immersed in history! Do take a tour of the Alcazar de Colon, Columbus' son's palace. The tours are well organized and extremely good. You can tour by yourself, but the young guides do such a good job and most speak English. Do take DR1's suggestion for eating at Briciola. This is my favorite restaurant. Have a great trip!

Natasha