After living in Florida for about 17 years, my advice is to get the Sunpass (you may use it more then you think) and exit I-95 and get onto the turnpike at Ft Pierce. Take the Homestead extension of the Turnpike. Takes you right to Hwy 1 in Homestead.
There are no tolls on Hwy 1 in the Keys. There is a toll if you take Card Sound Road out of Homestead down into the Keys.
I do agree with all the others that you do not HAVE to use the Turnpike or get Sunpass. Just take I-95. But I have noticed over the years, that in general, the folks driving on tollways down here seem to exhibit a little better driving behavior then those on other primary roads.
My .02