The resort is very compact with limited parking- so they have never encouraged non-guests to drive over to the resort (you have to cross a small bridge and enter thru a security gate).
If you are in the area, I'm sure the resort would be happy to allow a casual visit, but there is no sales presence at the resort (the sales office closed a few years ago) and since it is a sold out resort, there is no need to encourage more sales.
I'd suggest stopping in on a Friday (the heaviest day for check-outs) between 1-2pm. You can pull up to the gate and use the intercom to see if the desk staff would allow a brief visit. If they have any unoccupied rooms that have been cleaned already, I'm sure they'll allow a visit to get a feel for the resort. The resort is usually at 100% occupancy thruout the summer, so stopping mid-week will probably not have any vacant villas to see.
As already suggested, you can certainly park across the bridge and walk over to the resort (it's about 75 yards) without needing to ask permission. You can walk up to the desk and see if there are any clean villas to see- they will likely provide some information about the resort and HH in general. This is true for all of the sold-out
DVC resorts- tours of the villas are always based on availability and the front desk will have control of whether there is something cleaned to see. You would be welcome to walk around the resort at any rate. You could visit the Community Hall, Tide-Me-Over snack bar, general store, exercise room, see the pool and the dock area without any problem.
HH is the smalllest DVC resort and a walking tour is easily accomplished in a short period of time. As already noted, the Beach House may not be accessible, since you'd need a ssecurity pass to even enter the area by car and then a guest room ID to access the doors to the facility. You cuold certanly walk to the beach (like many guests choose to do) and see the beach (there is a public access area thru the DVC Beach House). You can even purchase food at the DVC snack bar there.
HH is a good drive from Myrtle Beach, so I'd sure plan ahead if you want to visit.
Enjoy!