Hi, Kirsten .
The correct translation for "Entre dos tierras" is "Between two lands".
The translation for Between two worlds" is "Entre dos mundos", this one have a more abstract meaning that maybe it will fit better for your purpose.
I don't know this song,.Have you the lyrics in hand? It would help to found out what exactly they meant.
Let me know if you need some more help.
PM or email me whenever you want.

Hope you let us know when your site is done!

Anna