Ricardo,
There's 2 possible fixes for this. We have a fix for a specific issue in the upcoming 4.0 release which can fix a language translation problem on some sites, depending on how things are configured. We can definitely give you that code change if you'd like, which is good if you have multiple languages in use on your site.
However, the easiest way, if you only use one language, is to use the language setting in the Facebook API tab of the JFBConnect configuration area. In the language box, simply put in pt_BR, and that will fix the language instead of trying to auto-detect it.
Hope that helps, but if you still have issues, let us know!