I have horrible neighbors, and a fence that's only three feet high. We
need a fence that will block them out _completely_, and stockade type fences
are extremely expensive.
I had an idea to make a "vine fence". I thought I would buy some wire (like
chicken wire, but thicker and sturdier) about 6 feet high, and put it down the
length of the yard using posts or stakes.
I live in PA,

This idea is widely recommended in the gardening literature. However, I would
only rely on annual vines for the first year. You want to plant perennials for
the long run. I don't know what zone you are in, but something evergreen would
be ideal. Avoid trumpet creeper, English ivy, or anything else that is
uncontrollably invasive. Patience with a vine that is a little slower growing
will pay off in the end. I wouldn't use climbing roses for that. They are a lot
of work, and not useful for your purpose for much of the year. Call your local
extension office. They can probably give you a list of the best vines for your
area. One that comes to mind is Dutchman's pipe, Aristolochia. It is widely
recommended as a screening vine in the Northeast.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"A tree never hits an automobile except in self defense." - Woody Allen