Puerto Rico for a day

I am travelling to St Martin later this year and on my trip home, have
most of the day (9:00AM until 3:00PM) in San Juan, due to an early
flight out of SXM and a late flight out of SJU. Does anybody have any
suggestions for spending part of the day in San Juan doing something fun
rather than sitting at the airport?

Thanks,
Paul

Going to Old San Juan will cost at least $32 rt by taxi. Taxi will
take around 20 -25 minutes which leaves you plenty of time to see OSJ.
You can use public transportation (bus) that costs $1 or less each
way. I have never used a bus but I am reasonably certain the trip
will take at least] one hour.

On a similar stop I rented a car for 30 bucks and went to the rain forest
(El Yunco or something like that) then came back to the airport in time for
the flight , more fun than shopping in the airport.
If you go to old san juan by a rental car make sure you park far from the
castle & then walk to it , coz if you get into the circular drive there will
be a lot of traffic and NO exit , you may be stuck for more than an hour ,
same thing if you are taking a cab back to airport take it in the directioon
going towards the airport from the beginning, not one that will make a u
turn.