They have areas outside the park but not within the park
For information and to learn when the "Medano Pass Primative Road" is open check out: https://www.nps.gov/grsa/planyourvisit/medano-pass-road.htm Be sure to bring a pressure gauge and a portable compressor tire pump if you're planning to start at the sand dunes and take the primitive road west to east so that you can air your tires up to full pressure for the rocky road ahead after deflating them for the first few miles of soft deep sand
Previously answered above...
The four-wheel-drive Road just past the campground inside the park is closed this time of year but during the summer it's a great place to access the backcountry. You cannot take motorized vehicles on the dunes
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