Ditto on that, especially south of Orlando. Tho it can be bad north of Orlando too. US 19 is also very bad south of Crystal Springs.
Maybe take I-75 and get off and explore towns along the way. Once you get to Ft Myers, take US 41 across the Everglades. You can do the Shark Valley entrance to the parks and take the tram ride. There's airboat rides all along there too if that appeals to you. I would not recommend the loop road if you are pulling a RV or are in a Class A.
At the as you get near to Miami, you'll see an Indian Casino, turn onto Krome Ave (177th) and follow that south. Lots of fruit stands and such, it runs into US 1 in Homestead, take that down to the Keys.