SPANISH Translation

Hi there, this is a nightmare!

The thing is: recently I update the theme and all that was translated manually back to english “load more posts”, “read more”, “posted by” and so on… what can I do in order to translate update friendly?

I have 3 more sites (differents companies) so I dont know if editing wp-config would be the better option. Is there an option to change only your theme to spanish using your .po files?

Take a look

http://pleigraun.com/uberfobia/
http://pleigraun.com/blog-masonry/
http://pleigraun.com/ (carrousel)