Hi Carlos,
Thank you for your message, it is encouraging! I have not been working
on the project for the past weeks, but I'd still very much like to see
it happen - SICP subtitles completed.
If you want to have control over things, I can add you to our Google
code project which has an SVN server to serve the files:
http://code.google.com/p/sicp-subtitles
However, if you do not want to go into all that - there is no need. If
you just email us a spansih translation, we will include it in the
project and acknowledge your contribution.
Yours,
--Anton