What zone 6 fruit or flowering plants make good "wall" between yards?

Depending on how much privacy you want/need, sunflowers are a very inexpensive way to make a temporary "wall". Try using the varieties that produce multiple heads for a longer bloom time. Added bonus, the neighborhood birds will love it!

Do you want annuals or perennials?

Try lorapetalum aka pink fringe flower. Mine are now 6' tall. Keep them shaped but do not prune in the fall or you won't have spring flowers. Beautiful year-round foliage.

I personally love the look of wild rose shrubs. They smell wonderful, are very hardy, bloom all Summer and into the Fall and grow about 5' high. I also am fond of Japanese Quince but, unfortunately, the local rabbits like them as well ... so they never reach their normal height. Snowball bush is lovely too but can grow quite wide so if your yard is narrow, you might want to pass on that.

I wonder if corn stalk borders would work? I want to do my backyard with it. Dual purpose👍