Westany have done some Spanish languages and Mexican Spanish - http://www.star2billing.com/products/voice-prompts/
The soundfiles are in the a2billing tarball, along with a script.
Additionally, you will need the digits, which are usually found in /var/lib/asterisk/sounds/es/digits, there are about 120 recordings in there.
Formats, to avoid transcoding should probably be in at least:-
These are the most common formats.
I use NCH Wavepad to do format conversions,
Thanks Jose for the heads up, found the script, and regarding the voices in south America we generally hate Accentted voices like mexican (only good in soup operas) the worst of of Gallego or spanish from spain because of their different terminology and pounding of the language.
I'll have a look at it and after I got them mastered in my recording studio for a good quality where should I submit them?.