Mariner Minors passed along this link stating that Campillo has now actually signed with the Mariners. My knowledge of Spanish is, in the words of an old professor, "not horrible," so here's an attempt at translating the important parts of the article:
Jorge signed a contract yesterday with the Seattle Mariners, and the organization welcomed him to camp in Peoria, Arizona.
The man who captured all the attention during the regular season for his impressive streak of ten wins without losing for the Tomateros also received notice that he'll be on the 40-man roster.
The article goes on to mention that he will be assigned to Tacoma to start the season. No word yet on who was/will be removed from the 40-man roster to make room for Campillo.
His numbers show good control with a marginal strikeout rate. I don't know a thing about his repertoire, and he's spent a lot of time in hitters' environments, but I'm going to remain skeptically intrigued for the time being.
Jeff's note, which is really J's note: we're still awaiting official confirmation, or at least something in English, so don't take this as fact quite yet.