Here is a sample itinerary for a 1, 2 ,3 or 4 day trip to San Juan, Puerto Rico.
Day 1 :
On 1st Day of your trip, visit El Morro fort. It is a spectacular monument. You can lunch at one of the many fantastic open air restaurants in the area. You can spend afternoon either walking around in old San Juan town or take free hop-on-hop-off shuttle and explore this charming town. There is awesome 17th century Spanish architecture and great shopping too.
On day 2 of your trip visit El Yunque rain forest. It is about 40-50 min drive from San Juan. They are located in a beautiful town called Rio Grande. It is an incredible rain-forest. There are many waterfalls in dense forests. To reach to some of the water falls you will need to do little hiking, while some of the water falls are visible while driving. You can stop the cars on side and enjoy the view. There are spectacular views of ocean at the top.
Spend 3rd day either relaxing at beach or enjoy tons of activities that San Juan beaches has to offer like Kite Flying, Snorkeling, Boogey Boarding, Kayaking etc. Trip to San Juan won't be complete without visiting one of its bioluminescence beaches. There are trips available for people knowing kayaking. If you do not know kayaking, there are some tours available in motor boats as well. These are living organisms emitting beautiful light during the night in the sea. It is once in a lifetime experience. Make sure to book your excursion atleast 5-7 days in advance. These trips gets full very quickly.
Spend 4th day shopping unique Puerto Rican cloths, gift artifacts, candies and coffee.