Filter menu_tree_all_data() tree by language?
I suppose you have i18n_menu.module installed. In this case, use i18n_menu_localize_tree($MENU_TREE) to get the tree for the current language.

To get secondary menu, for instance (on template.php):

$tree = menu_tree_all_data('menu-secondary');
$variables['secondary_menu_expanded'] = menu_tree_output(i18n_menu_localize_tree($tree));