hi,
1-Open the product details' PHP file:
/templates/YOUR_TEMPLATE/html/com_virtuemart/productdetails/default.php
/templates/YOUR_TEMPLATE/html/com_virtuemart/productdetails/flexv2.php
FYI: There are 2 layouts: default and flexv2. Make your modifications only on the file that you are currently using.
2- find this line:
js.src = "//connect.facebook.net/en_US/all.js#xfbml=1";
and replace it with this:
js.src = "//connect.facebook.net/<?php
$lang = JFactory::getLanguage();
echo $lang->getTag(); // this prints the Joomla's current language unicode, i.e: en_us, it_IT or es_ES
?>/all.js#xfbml=1";
So, depends on your Joomla's current language, the Facebook SDK will also be translated. For more info about Facebook SDK, see this page: developers.facebook.com/docs/javascript/quickstart/v2.5
Regards.