I'm in Washington state - hello neighbor.
There are some native trees that would be hardy and healthy in your
location- well, actually southern oregon ranges from rainforest to desert,
so I'm not sure exactly where you are, but I'm sort of assuming
Ashland/Medford area or else Klamath Falls.
Anyway, you could consider the Oregon big leaf maple, the Oregon Garry
Oak, native species of alder, native dogwood, etc. The advantage of any of
these would be minimal maintenaince after they are established (one year of
irrigation, then they'd be on their own). Non-natives that grow well in
Oregon are things like Catalpa (pretty flowers in July, HUGE heart-shaped
leaves), linden, black locust (although this suckers profusely), several
varieties of oak and maple. You could mix in a few evergreen flowering
trees - the native madrone, evergreen magnolia, a tall variety of English
holly - to give you some privacy during winter months.
Good luck.
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