No, however you might want to pursue getting your neighbor to do their side as well. Make sure you prime. And Duration is a great product from Sherwin Williams.
Instead of painting you should use a stain. For a "painted" look choose a solid colored stain. I like Superdeck 9600 series. It is an emulsified oil/acrylic and is water based.
I agree that it is best to stain both sides. But with a stain you could get away with only doing one side as a stain will breath more than a paint.