When it comes to Florida the population and the traffic increase significantly during the winter. I took off on a cross-country tour. From Vero Beach I took highway sixty? to Yeehaw Junction. From there I got on highway 27 going north. 27 had shoulders, yes, completely covered with coarse and fine gravel. Mufflers, sticks, car parts, and many kinds of debris covered most all the shoulder surfaces making them useless for a loaded touring bike with high pressure tires. The useless shoulders force the cyclist to use the main motorized part of the road.The traffic at many times looked like a train going by. It was that dense. It was extremely loud and fast. Hours of bicycle riding in those conditions, especially if it is day after day, can be nerve wracking, not to mention the fact that it might increase your chances of getting hit.
Highway 27 has been there for decades. If they have renewed it or cleaned off the shoulders in areas, that's good. I have not seen it recommended on any bicycle maps. It might be ok in some areas in summer when traffic is not so thick, but where I was at that time of year I got off it at the first opportunity. I not only do not recommend it where I used it, but I strongly advise any cyclist to avoid it.
441 to Okeechobee and around the lake might be a good way to go. From Moore Haven take local roads to Fort Myers and south to Naples. Or, from Moore Haven you can take local roads to near Everglades City and go east on Tamiami Trail across the everglades to Miami. You might want to avoid going directly into Miami by going east of the large gambling casino. It had a reputation for being a high crime area when I went through there.