Genesis is clear that the knowledge of God passed from generation to generation, presumably by parents teachings children and by neighbors teaching neighbors. It's obvious that Eve continued to recognize the presence and hand of God in her life (Gn. 4.1, 25). Genesis 4.26 tells us that people were calling upon the name of the Lord—invoking His presence. In Genesis 5, we can tell that the passing on of religious truth is still happening, since Enoch (Gn. 5.22-24) knows the Father, as does Noah after him.

So, yes, such knowledge is being passed down the family line but also through preaching (2 Pet. 2.5) to one's neighbors.

How did pre-Abrahamic believers come to know the Father?

I know that Romans 1:20 tells us that all people can see proof of the Father in creation itself (the earth and sky), but barring this, how exactly did those that the Father found righteous, yet came before Abraham, come to know the Father? Did Adam pass down his knowledge of the Father down his family line? I know Noah was found righteous; was this simply because the Father spoke to him like He did many other people in the Bible?