It can be confusing sometimes. I used to live in San Diego (not a californian though), and if you live in the county of San Diego you say that you live in San Diego. It's a pretty big county with some cattle farms so I thought I should ask. I dont know how to explain it but living in California is a different experience, it narrows your view a bit I think.
Anyway, living in a state with cold winters you would probably want an enclosed shelter with insulation and power so the ducks can always have unfrozen water when the temps drop. I dont have any idea what your predator situation is like, here in Washington my biggest problem is going to be raccoons. Our property is fenced so loose dogs aren't an issue and the hawks should only be a problem while the ducks are small. We are building a duck house with fully wired floors to prevent digging in. We are also going to put large rocks around the foundation for a little more deterrent and possibly hotwire around the yard fence.