I'm pretty sure all you have to do is set both the blog's and author's locale to the language you want. Blog #1 is an aggregator blog, so it will be in whatever language it has selected, but posts will always be in the language of the author.

b2evolution doesn't translate posts, so the 'stock' text on the page is in the blog's locale/language. Stock text for each post (like where it says "comments" or "author" or "words") will be in the author's locale/language.

I set the blog locale to the correct language. But the problem with the author locale is that it will be only one author for each blog.
The other people only will can read the messages.
So that I want is the visitors are redirected to their language blog based on the language of the navigator.
So they don't need to click on the link for their respective language.
You can take a look on www.els-poblets.info and see what I did, that's 4 blogs with 4 different language (actually are 2 working language, spanish doesn't work and I should translate valencia).
So the visitors can be redirected to their languae bloc or only can do that with authors?
I don't need the messages being trasnlated automatically, I have different bloggers for their language.
Thanks

andrago wrote:

So that I want is the visitors are redirected to their language blog based on the language of the navigator.

That shouldn't too hard. Just get the HTTP_ACCEPT_LANGUAGE header, sort the languages allowed by quality factor, etc., and then redirect based on that. It could be done in PHP fairly easily (though the $_SERVER array). In JavaScript, you can also use navigator.language in Netscape and compatibles and navigator.userLanguage in IE to get the language of the browser, which might be different than the preferred language.