Form built by Ajax commands not sending values
You need to build conditional elements in the form definition (mymodule_form) and not in the ajax callback. When the form is rebuilt using ajax, $form_state['values'] will be set, whereas it's not set on the initial form build.

Here is an example:

function mymodule_form($form, &amp;$form_state)
{
  if(isset($form_state['values'])
  {
    // put your conditional form elements here
  }
}