If you arriving same day, in the airport as you leave you have a few options... a taxi has a set gov't. fee if you and your luggage can fit into one. there also is a bus option, which is cheaper, but you must wait for the bus to fill. Carnival works the same way.... a rep. with a carnival flyer gets you to pay aprox. $15pp with any amt. of luggage and you wait for it to fill. You can get a limo for $20pp plus tip. I believe you can contact carnival prior and schedule this, it saves you one more line.
please know that the $$ amts are almost 2 years old from when we've sailed. Know that you have many options upon exiting the airport. We always fly in the day before in san juan (having come from buffalo with the weather) and have viewed the options, only taking a taxi to our hotel.
From memory, the ride is 15 minutes.
Doing the bus, your luggage is automatically loaded, no porter additional charge. taxi and limo equal porters. Someone please correct this if it's changed, but 5 cruises in, I've not seen a varriance in the embarking proceedure and we've done it all.