Ok, I've got some news from the author: Thanks very much Gerardo !!!
===============================================================
What I did to add more filter options was to add a few lines in "template_portfolio.php",
Guessing that you already have the categories to use to filter your entries you have to look for the "Slug" of each categorie..
e.g. mine are: basico, medio, avanzado
Then you have to add the following code to your template_portfolio:
AFTER this code:
-------------------------------------
if (isset($categories[1])){ $hide = ""; }
$output .= "<div class='sort_by_cat $hide '>";
$output .= "<span>".__('Filtrar por tipo:','avisio')."</span>";
$output .= "".__('Todos','avisio')."";
foreach($categories as $category)
{
$output .= "category_nicename."_sort'>".$category->cat_name."";
}
$output .= "</div>";
------------------------------------
You have to add a code from link below: (when i tried to paste it here, some words were cut.
http://www.codeupload.com/3861
-------------------
The id for each link should be your categorie slug + "_sort"
=============================================================
I've tested this option and can say that partially works for me, but it's better that somebody else would analyze it, because I'm not the coder ;)
For example: let's say I've got something similar like it's written below
1 level filter: ALL, AUDI, BMW, HONDA
2 level filter: NEW, USED
When I click ALL and next select NEW or USED, everything works perfect !
But if I click AUDI or BMW or HONDA and choose NEW or USED it doesn't work.
Dude, what do You think about this code?
Previously You wrote that it's a major modification, now we have got a few lines which partially work. Would You please test it and say Your opinion about it ?
Create a new thread and tell me what problems you are encountering and what you want to know. 
There is no step 3 :) 
