Making geolocated latitude/longitude values available to computed field in Drupal 7
I think I was assuming locations are geolocated on edit/changes and that's saved to DB, which appears to not be the case. At any rate, I was able to use the location ID from $field_info to load the location, which then has the lat/long data I need:

$loc = location_load_location($field_info['lid']);
$longitude = $loc['longitude'];
$latitude = $loc['latitude'];


That was annoying...