Don't think so
I used to ride Marco when I was a kid and it was sparesely populated. My grandparents had one of the first houses on the island. Haven't been there in a few years, but Marco has been overpopulated for at least 20 years, mostly by senior-citizen snowbirds, and the little old ladies who can barely see over the dashboard of their Cadillacs are a serious danger. I've nearly been run over walking, driving and biking. I love my grandma, but she shouldn't be driving anymore, and neither should at least 10% of the people on Marco. (OK, gross generalization, but you get my point - even if it's only 2%, there are a lot of Cadillacs rolling around down there without proper guidance.)
That said, if I was heading down there again, I'd probably find someplace to ride...I just can't think right now where it would be.