I went ahead and got the UTV Permanent Highway Permit for a one-time fee of $9, now both a on-highway license plate and the on-highway decal-both have to be displayed along with the off-road permit decal. If you get caught with a expired off-road permit you will be ticketed and all law enforcement can write you up, from the Fed and State Forest departments, NM Game and Fish and the other law enforcements. As stated before, the NM Counties can have different rules for on-highway use, so it is wise to check 1st before you venture out onto a Secondary State Highway. Some of NM State Parks do allow the use of UTV's Only (No ATV'S) inside the boundary of a State Park but the UTV has to have the New NM on-Highway permit, off-road registration, Insurance, turn signals and a horn, eye protection too. At least in NM the off-road registration is good for 2 yrs but still close to $50.
Rocky Mountain atv is one place that carries the turn-signal/horn kits.