I found one last week while hiking. Public hunting area. Field the size of a football field, surrounded by trees (cut down the wind), no houses, no wires, mostly open ground.
first pic is ground level, other is from unit (UDI HD+)
I usually just fly at my local park if no one is around and keep it close. But if i ever want to try pushing my limits with LoS there is a decent size regional park about 10 minutes from my house with an "undefined air field" that a lot of people go to fly models and quads. (El Dorado) in Long Beach, CA. As you can see the huge open space in the center of the park. :]