Although most people will figure it out, the highway numbers are backwards. It should read: All trailheads are reached from either US14 (Greybull to Sheridan via Granite Pass) or US16 (Worland to Buffalo via Powder River Pass).
You can get a shower for $2 at the YMCA of the Bighorns, which is located on rt 16 on the east side of the mountains roughly a dozen miles out of Buffalo. Very clean.