Hi Henry,

Since you have most of the day in San Juan, why not rent a car that can
be dropped off at the airport? If that doesn't appeal, perhaps a taxi to
the airport for an early check-in and then jump on the city bus back to
town. The distance is short (10 miles) and the view from the bus is just
fine.

I have always found that I can leave bags with the bell-boy in any large
hotel (Wyndham Old San Juan) which you might find to be the easiest
solution.

For more details and maps, see:
http://www.maxpages.com/caribbean/San_Juan

Aloha