I came to give you very good news!
The game in Spanish is ready and you can play in Spanish.
If you have a game in your library, but don't know how to change?
I'll help you, just go to your library, go to your games list and look for the Mix-sign there, then right-click and there will appear the steam configuration. And at the end there is a language tab and you select "Spanish".
P.S.: If text is wrong or bug, you can send a message about it. ( =>w0)/"')