You can take a break from Rte 6 by following some of the beach roads in Wellfleet and Truro. A couple of them loop by the Hollows and then rejoin 6 a little farther along towards P-town. Check your bike maps. In North Truro, you can try 6-A along the bay shore.
Another option is to ride back towards Barnstable from Orleans, by following Rte 6-A. If you want a slice of what Cape Cod must have been like before tourism changed it. It's a beautiful ride, along rolling hills. Not as heavily traveled as Rtes 6 and 28.
Don't trust your bikes unlocked at night, or even when you're in a restaurant. Cape Cod has a lot of drug-related crime now. Orleans has its share of that, too.