We've flown into FLL and sailed out of Miami twice. The first time, we uses SAS because they were highly recommended here on the DIS. It's interesting to note that they have more than a few bad reviews on Yelp. We flew in, used SAS to Miami and stayed downtown. The next morning we took a taxi to port. It worked great! Unfortunately, on the way back it wasn't so great. The driver was extremely unsafe in his driving. He was going very fast (much faster than the flow of traffic) and was weaving in and out of lanes, no blinker. I've driven with tamer NYC cabbies and let me tell you, I have had some pretty insane taxi rides in Mexico. This was not okay.
So the second time around, I was not going to use SAS again. That time we rented a car, drove to a hotel in FLL, stayed there, then returned the car to Avis the next day in downtown Miami and took the Avis shuttle to the port. The price difference between the two was a wash.
I will probably use Jiffy Jeff next time if we do it again. I liked staying in downtown Miami. It was easy to walk to dinner and other activities the night before the cruise.