I've just come home from a vacation on Cape Cod (sob) and spent a lot of time riding their super-awesome bike trails. Check out my review here. Well, it's less a review of the trails than of the humanity upon the trails. I even did the P'town loop, it was a good length but pretty hilly and hot (through the sand dunes). So stick with the Dennis-to-Wellfleet trail if you're just looking for a cruise. Or a run-in with all the many personalities who populate summer vacation.