There are people that ride US 80 between Tybee and Bull River. There are people that BASE jump too. I won't do either. Maybe early on a weekday morning it may be OK. I've only seen it on weekends and later in the day.

Yes that trail is only good for jogging or cruising, not for a roadie.

Here's a thought though; You are on vacation. Relax for a week. Rent a cruiser and ride the beach. Get a rental kayak and explore the Back River and Little Tybee.