Ornamental hops can run from tea hops with almost zero alpha acids to a few high-AA types that put out long sidearms. After you check for lupin, I'd boil a few in a quart of water, pouring off a little of the tea at 5 minutes, 15 minutes and 60. If you chill them immediately after pouring, you'll have a better idea of the characteristics.
Or you could just brew a trial beer. I made Ditch Witch a couple years ago from some hops growing in my neighbor's drainage ditch. His grandfather was a hop grower back in the 1920s. The beer was okay, but I think I'll stick to known hops. Plus, the hops are intermingled with blackberries and a pain to harvest.