Although the beach itself is public property, there's no easy public access as the beach resorts in this area of Nusa Dua are essentially in a compound with no free parking or convenient public transportation. The Laguna has a guardpost at the road entering the property and the Westin has a similar arrangement. [There's a temple located on the boundary between these hotels, so I don't think local public access is totally forbidden.] IIRC there are also some hotel cabana type thingies on the beach, available for rent by hotel guests and clearly provided/staffed by the hotel. You won't generally see crowds of people on the beach who aren't hotel guests, but I think there might be some local festivals that involve everyone going to the beach on a few special days.