While there isn't an exact English translation that's a common prayer, it's closely aligned with the English Catholic hymn "Ave Maria" which translates to "Hail Mary."
Here's the full text of "Ave Maria":
Ave Maria
Hail Mary, full of grace,
The Lord is with thee.
Blessed art thou among women,
And blessed is the fruit of thy womb, Jesus.
Holy Mary, Mother of God,
Pray for us sinners,
Now and at the hour of our death. Amen.
So, while "Witaj królowo nieba" is a Polish phrase, the closest English equivalent is "Ave Maria."