Is that Kermit? I have been riding the Oregon dunes for years, and love it. But I am moving to Austin very soon and I don't think Texas offers much in the way of sand dunes.
Best regards
-Jason
Its no glamis and lacks the beauty of ocean/pine trees/etc of the coastal oregon dunes, but Kermit can be pretty fun. its somewhere around 5-6000 acres, if you stay on the northwest side its free, but its just you and the dunes, no amenities. Waynoka is pretty fun time too. there are supposedly some dunes in the corpus christi/south padre / area, but have found any solid info and i think maybe now closed.
in the austin ish area, I hear great things about Marble falls for trail riding.