Using taxonomy terms alias in views contextual filters
Finally my work around this was as it follows:


I created a custom taxonomy vocabulary which has an extra field "human friendly tag".
I changed the name of all the taxonomy terms for being seo-friendly (not spanish accents, nor brackets and so forth).
I use term name for the internal stuff in my view (term names are part of the url). You can see how to get this here as @RobW pointed out. 
I use the first field (the "human friendly tag") when content is rendered (in the view). I need to use "rewrite results" options when creating the view. 


I hope it is clear enough. :-)