All the strings that are displayed in the FogBugz UI are localized based on your site's default language (Admin -> Site Configuration -> Regional -> Language).
That being said, a number of our translations are out of date and/or incomplete. This article has more details.
As a workaround, you could include some JavaScript in your Wiki Template that patches up these strings:
var rgMenuTitles = [
'Page collections fixed',
'Attributes fixed',
'Hierarchy fixed'
];
var sNewArticleText = 'New Article Fixed';
var rgPageCollections = [
[400, 'Title Index Fixed', 'title_index.png'],
[300, 'Recently Changed Fixed', 'recent.png'],
[200, 'Page Hierarchy Fixed', 'hierarchy.png'],
[100, 'Incomplete Fixed', 'incomplete.png']
];
var rgAttributes = [
[100, 'Tags Fixed', 'tags.png']
];
// fix up the section titles
$('div.wiki-page-browse-menu-title').each(function(ix, el){
$(this).text(rgMenuTitles[ix]);
});
// fix up the new article link text
$('li.wiki-page-browse-new a').text(sNewArticleText);
// fix up the "page collection" links
for(var ix = 0; ix < rgPageCollections.length; ix++){
$('ul.wiki-page-browse-menu:eq(1) li[ixpriority="' + rgPageCollections[ix][0] + '"] a')
.html('<img title="' + rgPageCollections[ix][1] + '" alt="' + rgPageCollections[ix][1]+ '" src="default.asp?pg=pgPluginStatic&sPluginId=WikiNavigationPlugin@fogcreek.com&sFilename=img%2f' + rgPageCollections[ix][2] + '"> ' + rgPageCollections[ix][1]);
}
// fix up the "attrubtes" links
for(var ix = 0; ix < rgAttributes.length; ix++){
$('ul.wiki-page-browse-menu:eq(2) li[ixpriority="' + rgAttributes[ix][0] + '"] a')
.html('<img title="' + rgAttributes[ix][1] + '" alt="' + rgAttributes[ix][1]+ '" src="default.asp?pg=pgPluginStatic&sPluginId=WikiNavigationPlugin@fogcreek.com&sFilename=img%2f' + rgAttributes[ix][2] + '"> ' + rgAttributes[ix][1]);
}
It's not a particularly pretty fix, but hopefully it's enough to get you going.