How to output every second grouping in views?
This seems like a good use-case for a theme override.

If you click the "advanced" section in the view and click "Theme Information" at the bottom, you'll get a list of theme names. Click on "Style output" and copy the code, and paste it into a file in your theme folder with the most specific name possible (at the end of the list starting with "views-view-unformatted.tpl.php").

Not sure if there's a more elegant way to get a row count (it doesn't seem to be an available tpl variable) but you can DIY like so:

  &lt;?php function count_this_view() {
    static $count = 0;
    return $count++;
  }?&gt;


Then wrap your tpl in a conditional like

  &lt;php if (count_this_view() % 2) :?&gt;