We did a 7 night cruise onboard Celebrity Summit in November 2011 to/from San Juan & had one night pre-cruise accomm (booked direct via
www.priorityclub.com) at the Holiday Inn Express SJU.
The average taxi fare seemed to be approx USD15.00 for our journeys:
a) SJU Airport to Holiday Inn Express
b) Holiday Inn Express to Plaza Las Americas (large shopping mall)
c) Plaza Las Americas to Pan American Pier where ship was berthed
It was maybe USD25.00 from the Pan American Pier to SJU Airport at the end of the cruise, I forget exactly but it wasn't an excessive amount.
We had flown LAS/xDFW/xMIA/SJU (KUPP fare
) but AA misplaced our luggage so we had to buy some new stuff as we didn't know when we'd get our bags back.
If flying out of SJU the same day the cruise arrives back I would book a flight mid-afternoon as despite the ship docking at 0600, they didn't start disembarking the first group of pax until 0830. Our 'muster' time to disembark was 0915 but we didn't start to disembark until 1030 due to the long queues in customs.
We ended up arrived at SJU Airport at 1115 for a 1245 departure which IMHO was cutting it a bit fine.
Note that when you fly from the US to SJU there's no customs on arrival as SJU is classed as domestic, however as your cruise visits ports in other countries you need to clear customs on arrival which takes time.
Definitely liaise with the concierge on the ship & let them know your flight details to get a decent priority when disembarking.
Cheers Oz