Sure you can. With php only (as wpml-config.xml does not include such option).
The code snippet below transforms all inputs to textarea.
add_filter('pll_get_strings', 'pll_get_strings', 20);
function pll_get_strings($strings) {
foreach($strings as $key => $string)
$strings[$key]['multiline'] = 1;
return $strings;
}