Ok wel it sounds to me like you essentially will have 2 of everything, 1 version in english, 1 in portuguese...
If you're going to do that i'd suggest having 2 top level categories..
English
- Category
- Category
Portuguese
- Category
- Category
Make you additional categories all sub-categories of either English or Portuguese...
Then in your sidebar file created 2 lists of categories, one that lists all sub-categories of ENG, and the other obviously grabs sub-categories of POR.
Then again perhaps the built in language support may be better suited, but this really depends how you're laying out the content i guess...
Are you planning to have duplicate articles, 1 for each language, or are you writing in 1 language and just translating the content...
I think you ideally need to decide how the content is to be managed before you go changing X, Y, and Z all over the place, if that makes sense...
Creating 2 lists that grab from 2 top level categories (as per the example) is simple enough, that i can help you with.... no problem there, but i have a feeling on the whole you're perhaps looking to do a little more then this...