Translation works only if you use the helper class for printing a string. 

`Mage::helper('xxxxxx')->__('Text to be translated')`

Before this line of code add an `if` condition to check if the current customer belongs to the group you needed. If so, use the above line of code, else, simply use PHP's echo function. So, the code may look like this:

    if (customer belongs to group) {
        echo Mage::helper('xxxxxx')->__('Text to be translated');
    } else {
        echo 'Text without translation';
    }