Went during Thanksgiving Break 2011 with whole family. Was a difficult hike for the smaller children with numerous elevation changes. But had fantastic views of the lake below. In the limestone on the trail there are numerous fossils and many fantastic rocks for the budding geologist. Many trails in the area and a fantastic display of wildlife.
From Lopez Lake, drive on Hi-Mountain Road until you turn left of Upper Lopez Road. Take this road until you get to the Boy Scout Camp on the left side of the road and walk through this property, following the Duna Vista signs. It's a rolling hike with some good steep areas. Mountain bikers also use this road and come flying down some of the hills. The top of Duna Vista will give a bench to sit on while viewing Lopez Lake, the dunes at Oceano and the Pacific Ocean. Beautiful. Great workout for sure. Bring lots of water, especially on a warm day.