Spanish language servers will be provided for new Latin America subscribers, but those already playing on the North American servers can download a Latin American Spanish "language pack," and even transfer to the new servers if they want to. Check out the FAQ for more info.
Oh, and Blizzard will be hosting a midnight launch party on the 25th at the Blockbuster at Av. Universidad #697 en México, D.F., followed by another event at Plaza Satelite in Estado de México. ¡Diviértase!