If you are a naval history enthusiast, an UNESCO World Heritage site enthusiast, or have a cheap flight/hotel/hostel combination, then, yes, go.
If it is your dream to go to Puerto Rico, then, yes, go.
I had a great time traipsing about Castillo San Felipe del Morro and Castillo San Cristobal and was entranced by the Bioluminescence Bay in Fajardo. But, for the budget-conscious traveler who stays at hostels, eats at food stalls, and uses public transportation, then, nay. Save your money for somewhere you really want to go.
There are few hostels in Old San Juan (historic city center), and there appear to be no hostels outside of the capital city. Hostelworld lists five hostels in San Juan, Puerto Rico. Hostelbookers lists two hostels in San Juan, Puerto Rico.
Old San Juan has many restaurants with a variety of cuisines, but most of the restaurants seem to cater to tourists and are priced accordingly. No food stalls, stands, or trucks.
Public Transportation From/To the Airport
There is no airport metro or airport shuttle bus from the San Juan Luis Munoz Marin International Airport to Old San Juan (historic city center). While you can go by bus from the airport to Old San Juan, you must take two buses: one bus from the airport to Isla Verde and one bus from Isla Verde to Old San Juan. The fare is $0.75.
But, the Tourist Office recommends allocating one to two hours for the journey as the bus drivers do not necessarily follow the bus timetables. You do not know how long the first bus will take to get to the transfer stop, and, at the transfer stop, you do not know how long you will have to wait for the second bus.
There are taxis with set fares from the airport to designated locations with an airport-monitored taxi stand. The set fare to Old San Juan is $19.00 plus a $2.00 airport fee.
For more information, check out these links:
Frommer’s – Puerto Rico Guide: http://www.frommers.com/destinations/puerto-rico
Frommer’s – Getting Around: http://www.frommers.com/destinations/puerto-rico/744387
Lonely Planet – Puerto Rico Guide: http://www.lonelyplanet.com/puerto-rico
Lonely Planet – Getting Around: http://www.lonelyplanet.com/puerto-rico/transport/getting-around