Definitely not legal in Florida but never seems to be enforced. I see people all the time riding bicycles with both ears plugged in to thier cell phone, some are driving, some on motorcycle, some walking. The reason for the rule is because you usually can't hear anything approaching if both your ears are plugged. Here in Wtr. Park I saw a young girl crash her bicycle because she didn't hear an ambulance coming up on her....both ears plugged in to her cell. The dummy almost got hit by another car.
I called around to some folks I still know in the LEO field John. Ear buds seem to be a loop hole in the law. It is not legal to cover both ears with enclosed headphones, like the ear muffs I wear working with the power tools. One of my friends said that ear buds seem to be OK based on the fact that tickets involving them are always thrown out hence most cops won't even bother. Judges seem to believe that they aren't covered by the law since they are not specifically mentioned because they really didn't exist when the law was written. As you know, I wear ear buds almost all the time when I ride, with some pretty heavy classic rock blaring away. Range may be an issue but I can still hear almost everything and carry on a conversation when stopped. Volume may indeed be a factor as well.
