If you want to search a spanish movie, just search with its original spanish title. If you want an english film, dubled in spanish, just search the movie's title with "spanish" or "espanyol" next to it (example: Titanic spanish). If you want subtitles in spanish, just go to http://www.opensubtitles.org or any other subtitles website, and search the subs for the film. Thats it.
you can search like that at any torrent website, but i usually use www.torrentz.eu