Should the gospel be preached to everyone?
No, the gospel is not to be preached to the Gentiles and Samaritans.
These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not: But go rather to the lost sheep of the house of Israel. Matthew 10:5-6
Yes, the gospel is to be preached to everyone, including the Gentiles and Samaritans.
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost. Matthew 28:19