I concur with newyorkgeorge. By the time you wait for the excruciatingly slow elevator to reach the third level, walk on the super-narrow, lumbering sidewalks, then take another slowpoke elevator down, you could have made it in the same amount of time by simply hoofing it.

As CokeandTaco has noted, when you reach the lower level of "E", you must exit the terminal building and cross the road (be careful, Florida drivers aren't always the most safety minded) to reach the bus stop (just a glassed-in waiting area). When you reach the Tri-Rail station area, don't waste any time - go immediately to the ticket booth and purchase your ticket, and walk around to the right to board the train. If the bus is late, as it often is, you may have very little time before the train departs.