How can you retrieve entries with a specific locale in a plugin?
You'll want to use an ElementCriteriaModel:

$criteria = craft()-&gt;elements-&gt;getCriteria(ElementType::Entry);
$criteria-&gt;id = $entryId;
$criteria-&gt;locale = $lang;
$entry = $criteria-&gt;first();

if ($entry)
{
    $response = array(
        'titre' =&gt; $entry-&gt;typeChambre,
        'etage' =&gt; $entry-&gt;etage-&gt;label,
        'surface' =&gt; $entry-&gt;surface,
        'loyer' =&gt; $entry-&gt;loyer,
        'charges' =&gt; $entry-&gt;charges,
        'description' =&gt; $entry-&gt;description,
        'photos' =&gt; $entry-&gt;photosChambre
    );

    $this-&gt;returnJson($response);
}