<label class="checkbox">
<input type="checkbox" id="user_ids_for_edit" name="user_ids_for_edit[]" data-toggle="checkbox" data-toggle="checkbox" value="14">Billy Joel
</label>

$.ajax({
   type: "GET",
   url: "/data/team_users",
   data: { id: data.id },
   cache: false,
   dataType: "json",
   success: function(response)
      {
        for (var user in response) {
            alert(response[user].id); // this gives the right user id, so my ajax call works...
            $('#user_ids_for_edit[value="'+ response[user].id +'"]').attr('checked', true);
        }

      }
});