Avaz can be used in Spanish by following the steps below: 
  1. Change the voice to Spanish.
  2. Download or save this Spanish vocabulary file to your Dropbox. If you don't have a Dropbox account, create a new account. 
  3. Restore the Spanish Vocabulary under Settings > Backup & restore. You can learn more in this article - How to restore vocabulary from Dropbox. Copy the Spanish vocabulary to Dropbox. And then follow the step 4 from the link above. 

Note: Only the picture vocabulary will be in Spanish but the rest of the app (buttons, messages in pop ups etc.) will remain in English.