319 should be avoided but Hwy 19 has very light traffic once you get out of town. Very busy in town but once you get outside the city traffic disappears. I wouldn't hesitate to ride it in terms of traffic. But it's a 4 lane with a wide median so it's not the most scenic road. Much nicer than an expressway, but not a bucolic country road.

Between 319 and 19 heading out of town to the south you have Metcalf Rd. and Magnolia Rd., which runs into Metcalf. Those are much prettier roads and have very little traffic. Metcalf Rd. to Magnolia Rd. is the route I would take by bike from Tallahassee.