Super Shuttle does not serve FLL. They only run within Miami-Dade County, although they wlll take you from Miami to FLL. There is a similar service that is based at FLL called Tri-County Airport Express. There web site is www.floridalimo.com. I think they charge $15.00/pp from FLL to the Port of Miami (Dodge Island).
The last few times I flew into Fll because it is cheaper. I usually take the share ride
program, which is just that you share a ride with other people, to Maimi for 15.00 dollars. I never had any problems with it.