Harry Potter and the Deathly Hallows (Book 7) is announced for publication in July (see, for instance, the HP encyclopedia: http://www.hp-lexicon.org/about/books/dh/book_dh.html ). I expect the official Spanish translation to appear some 2-3 months later - or perhaps even together with the English version, since they may already be working on the translation.

Here in Cochabamba, I have already seen a book which claims to be "Harry Potter, Book 7". Some non-authorized version, obviously, but I am not sure whether it is a translation of the "real" book, which somebody got hold of (JKR finished writing the book in January), or an entirely differnet story somebody just made up.

In any case, 'tis better to wait for the official release. I have seen non-official translations, which were obviously rushed to get to the street before the official release; one thing that caught my attention was that "Harry was lying on the bed" was translated as "Harry told a lie", when it is obvious from the context that he was "in a horizontal position". To mention just one royal blunder.