San Juan has huge vans as taxis, and they charge u similarly. Food options are not many in Old SJ Roads are narrower and driving is not as easy as it is in the US, though navigable. Make sure you have a GPS with TTS (voice) as the roads are packed close to one another The forts are very well maintained and beautiful.
Wish I had more time to explore SJ. Visited the El Yunque Rainforest by rental car. Hertz via Hotwire gave me a large car for $20 !! Car seats cost $13 extra each !