Although we have never had TCs refused around the Orlando area, if you travel further afield then you may encounter difficulties, certainly many places on the Keys won't accept TCs. Get them in relatively small denominations, as then the shop doesn't have to return much cash - thus less risk to themselves. Would suggest a Nationwide CC as the best option: relatively secure, best exchange rate & acceptable nearly everywhere + a small amount of cash for tolls, carparks and tips.