I vote for a screen of evergreen trees such as eastern red cedar or a type your local nursury will recommend. You can probably get some brought in with a tree spade for 2 to 3 hundred bucks per tree. If you buy smaller ones from the nursury, then double space them and trim out the middle ones as the others grow wider and bigger. You may want to go with a double layer with alternate spacing. And of course say goodbye to a big chunk of your backyard.