The sand dunes near Stovepipe wells are readily accessible from the road a mile or two east of 'town'. Though getting lost is probably not a huge risk (the dunes are relatively short and occupy a fairly small area) you could become disoriented and end up a long way from your car. Stay out of there in the summertime. The national park service newsletter documents the death of a reasonably well prepared hiker who succumbed to heat exhaustion and dehydration in just a few hours in the 110 degree heat. Hours later he died in a Las Vegas hospital, leaving his honeymoon bride alone in the desert. That is really bad form, in my opinion. We were there very early in the morning in mid November, temperatures in the low 50s to begin with. After an hour or so it warmed up enough to encourage us back to our vehicle.