Second and closer favorite: the bottoms along the Missouri and Yellowstone near the confluence, especially in spring and early fall.
No headsets, thanks, the motor is music to me.
I do not mind riding in a group, but prefer to be well at the back.
My hardtail ('82 Shovel in an old Drag Specialties frame) does not allow for being boxed in, and I have to avoid those little inconsistencies in the highway to avoid compression fractures. Tight formation flying doesn't give a guy much room to dodge the odd chuckhole.
Yeah -- I don't mind riding with folks, but I don't like tight "formations" except when riding with the PGR -- and that's for a good cause.