Don't be tempted to go through Tallahassee if you go that way; pass to the north on I-10.
US-19 from I-10 all the way down to Homosassa is perfectly fine four-lane with very little traffic until you get to the Crystal River / Homosassa area but it's not heavy traffic; just south of Homosassa you can jog over on US-98 and pick up the Suncoast Parkway down to Tampa. It's a toll road but not all that expensive. Do _not_ go any farther south on US-19.
I don't see any reason to go all the way over to I-75 with it's insane drivers.