If you get off of the island there is decent riding but on the island itself it's the bike path. I live here and don't go out on the island roads during the summer - off-season though, it's great.

The island itself is almost all resort-type parkway. 25mph streets, lots of stop signs.

However, if you go off the island, the roads are very flat. You can take US278 through Bluffton and either head towards Savannah or Beaufort (pro. “Byoo-fert”). It’s beautiful in that part of the world. If you go toward Beaufort, it’s a bit more rural with great scenery. If you use causeways and bridges, you might be able to get a bit of “hill work.”

I am in HHI next week as well. Any interest in meeting up to ride?

The hubs and I are here now. We brought our road bikes and biked the other day from where we're staying up the cross island bridge, and into Sea Pines to Harbor Town. We did have to hop on the bike path in order to get on the bridge, and the path itself is a multi use paved path, but the "path" on the bridge was more of a large side lane. Plenty of room. You can look on Strava or Garmin Connect at the heatmaps or segments to see where most people ride, that's how we figured out the route we took. We are staying off of 278, which has the multiuse path mostly on one side of the road, and during the busy hours it's kinda like any other road to be biking on. I prefer the road over the bike path, which is very windy, and can get congested with families riding beach bikes on it.

We have a vacation house in Sea Pines and I'm there I get up early (~6am) and go over the Bridge, out & back on the Cross Island Parkway and into Spanish Wells for a nice ride. One thing to remember - when people are on vacation, they leave their brains at home so be careful no matter when or where you ride. Call Alfred Olivetti, owner of Hilton Head Running (formerly Go Tri Sports) at 843-295-9565 and he can tell you about any group rides going on while you are there.