If metabox has content display content

You have to list the keys of the meta fields saved in the metabox, because their is no function to dynamically retrieve all the fields saved in specific metabox. For example:

$store_openingtimes_keys = array(
  '_cmb_open_monday', '_cmb_open_tuesday', '_cmb_open_wednesday', '_cmb_open_thursday',
  '_cmb_open_friday', '_cmb_open_saturday', '_cmb_open_sunday'
);
// all the not empty meta for the post
$meta = array_filter( get_post_custom($post->ID) );
// there are any not empty meta that is one of the store opening times?
$times_meta = array_intersect( array_keys($meta), $store_openingtimes_keys );
if ( ! empty($times_meta) ) { // if so, show content
   echo $content;
}