I suggest you the simplest way of going with a translation of one of
our
current posters:
http://fedorapeople.org/groups/designteam/Fedora%20Collateral/Posters/Fou...
We used the "4 foundations" theme at a few events this year and it was
successful.
Sources are available for Inkscape and Scribus, so translating is trivial.
Oh, and there is some ready-made Spanish language stuff from our amazing
Tatica: