I have ridden most of the ride from Homestead to Key West, it is a mixed bag. I used to ride there a few times a year, I stopped bringing my bike after one to many close calls.
Seriously DO NOT ride the section of US1 from Homestead to Key Largo, it is not meant for bikes and terrifying. The cars go 55-95mph and it is currently under construction. But you can take Card Sound Rd, it has much less traffic and is very scenic.
You'll rejoin Rt 1 in Key Largo, you can camp at John Pennekamp State Park. There you can go snorkelling, kayaking and scuba diving, which is cool.
From there you ride on a mixed route of side walk and bike path through Key Largo to Islamarado where you can jump on old Route 1 for about 10 miles, which is nice! Big shoulders and lots of bikes.
When that ends you get back on a mix of side walk and bike route.
The next place to camp along the way is Bahia Honda state park, which is so cool.
And from there its just a short trip to Key West.
The only problem with this ride is that the bike route is mostly the sidewalk that goes in from of all the businesses, which means lots of cars going in and out, not looking for bikes. Most of the cars are speeding and driving very aggressively.
It is a beautiful ride, its just not peaceful!
Good luck.
-Joe