This is alleged to be the best way to learn a foreign language. To those adults--young or old--I would say, "Hop to it."

Maybe they are, maybe they aren't. Maybe they can't afford a computer or lessons and it's going slow for them. Maybe they are learning disabled or have Down's. Who cares? Life is messy, everyone is different, and it's not for you to dictate no matter how entitled you feel to do so. About a third of this country's population live in areas where Spanish has been spoken since before the USA existed. If English speakers there want to assimilate, then they ought to learn Spanish...so hop to it, and so forth.