Were people from sheltered homes also following the world and the devil before they were saved?
Yes. Even those from a sheltered home life were included among all people before salvation. All were potentially in an environment, attitude, and lifestyle according to the course of this world and the prince of the power of the air, the devil, and had their manner of living in the desires of the flesh.
Les explains from verse 2 that before salvation every person, including someone raised in a sheltered home, was still in the same category. Even a sheltered home life did not remove a person from being potentially in that environment, attitude, and lifestyle according to the course of this world and the prince of the power of the air, identified as the old devil, Satan, the spirit now working in the children of disobedience. Among them, all had their manner of living in times past in the desires of the flesh and mind, fulfilling those desires. Paul did, you did, and I did, being by nature the old Adam nature. Earlier, the spirit part of us is dead because of sin but not gone; it needs regeneration, the work of the Spirit in salvation, to be made alive who were dead.
Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience: