To set Text to Speech in Spanish first Swipe down your notification shade and tap of the gear icon on the top right to take you to your settings menu> next scroll down to and tap on "general management"> then tap on "text to speech" > then tap on "Language"> here is where you can select Spanish as the language that your phone speaks when transcribing text.
You can also add a Spanish language pack by going back to the general management menu and selecting "language" at the top and adding a language pack (in this case, Spanish) as a secondary language for your system if you wanted.
