The trail is a great ride if you dont plan on going too fast. There's usually enough traffic on it to prevent it from being used as a race course, and through most parts there are frequent intersections and some of them are at major roads. But its mostly in the shade, so the sun isnt gonna be too oppressive.
If you ride the length of the trail, and dont have the energy to make it back, the number 19 bus will take you straight back to palm harbor. Pretty sadly though, if you can maintain a decent clip, you can ride from tarpon springs to downtown faster than a bus can make it.