As the package description says, there is no pt-BR translation available from Mozilla. If you use language-support-pt, then you'll automatically get the pt-PT one.
** Changed in: mozilla-firefox-locale-all (Ubuntu) Status: Unconfirmed => Rejected -- Package is empty https://launchpad.net/bugs/65223 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs