Well, it depends.
IMO, for 2 people, town car service makes the most sense. It is about the same as a cab (90-95, make sure you print out the coupons), but cleaner, no lines/waiting, and much faster than Mears shuttle which can make a lot of stops and take FOREVER. Look at the transportation boards for specifics.
You may also want to check rental car rates - if you can get a deal, that can be the cheapest way to go for a short trip - the last time I was down, I got a car for $19 a day including tax, so it was the cheapest option even looking at gas/tolls. (Of course, I stayed on-site and didn't have to worry about parking costs.)