Part of the intent with this release was to move the translation strings toward better WPML integration. It might take one or two more releases during the 2.9 release cycle to get everything right, though.
So, I do see where we can add a translation string for the dropdown. I think if you change line 82 in utilities.php (in the wpmem_create_formfield function) from this:
$str = $str . "<option value=\"$pieces\"" . wpmem_selected( $pieces, $valtochk, 'select' ) . ">$pieces</option>\n";
$str = $str . "<option value=\"$pieces\"" . wpmem_selected( $pieces, $valtochk, 'select' ) . ">" . __( $pieces, 'wp-members' ) . "</option>\n";
That would allow you to translate what displays to the user in the dropdown.
But I don't think you'll want to change the option values of either checkboxes or dropdowns. These are the values if the option is selected and they need to be compared against a value to determine if they are checked or selected. If that value is translated, that process may not work correctly.