// in the file functions/theme-head.php 

// find:
echo '<link rel="stylesheet" href="http://fonts.googleapis.com/css?family='. $gf_string .'">'."\n";
// replace with:
echo '<link rel="stylesheet" href="http://fonts.googleapis.com/css?family='. $gf_string .'&subset=latin,latin-ext">'."\n";

// find:
echo '<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=PT+Sans:b,r">'."\n";
// replace with:
echo '<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=PT+Sans:b,r&subset=latin,latin-ext">'."\n";

// find:
echo '<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=PT+Sans:b,r">'."\n";
// replace with:
echo '<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=PT+Sans:b,r&subset=latin,latin-ext">'."\n";