Although I don't have experience growing this in your area, I do grow it and it is a beautiful, tall, and dense bamboo that would screen very well. However, it is a clumping bamboo, and you would have to plant many large plants along the property line to get the screening you want now since each clump will only expand slowly in diameter over time. I am afraid that, if you wanted instant screen with this bamboo, you would have to spend thousands of dollars.

Thousands of dollars? Maybe not. I think the OP wanted to make a 40' wide screen. Let's say 5 plants at 8-feet apart, one-gallon potted starters, $100 tops.
I haven't grown bamboo in your area either, but in my garden, my F.Robusta is 8 feet wide after only 3 years. It has been very vigorous, true to its name. It is dense and upright in habit, but I think it will top out at approx. 15' tall.

tcstoehr-
I respect your viewpoint. However, I wasn't thinking of 1-gallon plants. The OP said he wanted a screen 20' high, and I am assuming he wants it soon rather than 5 years from now. That's why I inferred he would need large, mature pots, and those won't be cheap. I also see that he is in Zone 6, and I think that may prevent robusta from growing with the same vigor you're describing. Just my 2 cents....

Several weeks ago I was at Lowe's and saw some smallish Fargesia rufa being sold (maybe 1 foot tall/one gallon??) They were in the perennials section. There was only one prize listed in the whole area ($7.95 for all I thought). I selected about four Fargesia and preceded to checkout. Well, my total came to over $100.00 dollars (a lot of money for tall grass in my opinion--and I really am a bamboo lover). Convinced there was a mistake, I asked to speak to the manager. Sure enough, that was the price. I walked out annoyed and left the bamboo in the cart. When I got home, I started dividing the two Fargesias I already had in the ground so now I have a small hedge of Fargesia and Borinda angustifolia starting to develop. Now, they have just been there for a maybe a year, but they don't seem to be as fast growing as spreaders (such as Phyllostachys). Time will tell, maybe their pace will increase. They are in a great location (dappled sun mostly/some morning direct/relatively cool area under an oak). So the issues I see include; potential cost (even for little plant), moderate rate of growth, and the expectation to have a 20 foot tall screen without have to wait for years (if your neighbors are really spying on you, who want to wait a decade to do something about it?!). Do any Fargesia even get this tall? The other issue with Fargesia is that they dislike both excessive cold and heat (I believe they are subtropical mountain species mostly). The OP's St. Luis, Mid-Western location may be too extreme for it. I had to move mine from a sunnier/more exposed location to their current position. PS., At another end of the property (neighbors I do not like), I do have an island grove of Phyllostachys (nigra, aurea, vivax, and viridis) but this requires regular attention to rhizome pruning (which I do in early Spring and mid-/late Autumn.) Good luck!

Kudzu, I guess that's right, if time is really of the essence, which I don't know. But I would also guess that 20' tall is out of the question there as well.

tcstoehr-
I've got some pretty tall robusta, but it's only about 12'. After your last post I checked out the characteristics for it and it apparently tops out at about 16'...so you're right that this might not be a solution for the OP... especially in his Zone.