I tried to minimize exit hassles by saying I was going to ballparks and asking for a car that would not attract attention. The result, with 24,000 miles, had loose steering, brakes that pulled to one side, and not enough acceleration either to be assertive with the local drivers or to maintain speed on the mountain crossings. But the air conditioning worked fine. Do accompany the agent during the enumeration of scrapes and dents and keep a copy certifying the initial condition of the car. The road system is built to familiar US standards.
Drivers are macho, impatient, and indecisive.
On the secondary roads, you can easily get sidetracked by following a straight line instead of the good pavement. PR-14 between Aibonito and Coamo is twisty and unmarked for so long that I needed to stop and ask whether I was still on it. Speeds are in mph but distances and exit numbers are by kilometer. Maps are all a little out of date. The biggest disappointment is that Puerto Rico lacks the US system of motels at expressway exits.