How can I change a label text without interfering with an input radio inside the label?

Try this:

$('#myid').contents().last().replaceWith('my new text');

Put your text in a span and try this:

<label id="myid" class="inline">
    <input type="radio" value ="11">
    <span>my text</span>
</label>

$('#myid').find("span").text('my new text');

Check JSFiddle Demo