Tri-Rail is not really a "traditional" public transit system, but is really a work-commute-oriented system that (by design or happenstance) runs near the three area airports.
One thing you might do to help save time on arrival is to have an understanding of where the bus stops are at FLL (the signage is not the best). You may wish to contact the FLL airport authority and Tri-Rail to get instructions as the the exact location of the bus stop for the specific terminal that you will be arriving at:
http://www.broward.org/airport
http://www.tri-rail.com/