I see by the slope that drainage won't be a problem!
Also, I don't know the size of the deck above, but you could effect a partial screen with: a few potted shrubs (Skyrocket-types would work well here); some rail planters with both taller plants, annuals for starters(mini sunflowers)and trailing plants to partially shield the patio below, I.e., variegated vinca vine, sweet potato vine {black/chartreuse/tri-colour) Asparagus fern does well in containers and is both bushy and trailing if well watered; some taller marigolds if it's a sunny deck. Again, ask at local favourite garden store/nursery about narrow screening possibilities for the deck.
What kind of soil do you have? Clay or sand? Is it acidic? You may want to try some rhododendrons/azaleas underneath some taller crabapples or kousa-type dogwoods or other flowering trees: Golden rain or golden chain? Would you like a fruit tree? Or a nut tree? (beware of walnuts--they don't play nice with a lot of other plants.
This all looks like new construction, and sturdy, so you could put some decent sized hangers and hanging pots around the perimeter of the deck, also, to further the privacy.
Except for the latitude, you're in pretty much the same pickle I'm in--houses stacked on top of each other. Too bad we're not neighbours...but then, we'd never get anything done!
Hokay, maybe more later.
Happy Gardening!
Wing