How can I manually edit the search options in a facet block?
I decided to implement this by creating a new facet instead of editing an existing one.  This article describes the process.

The basic code looks like this:

/**
 * Implements hook_entity_property_info_alter().
 */
function MYMODULE_entity_property_info_alter(&amp;$info) {
  $info['user']['properties']['agg_gender'] = array(
    'type' =&gt; 'text',
    'label' =&gt; t('Search API Agg Gender'),
    'sanitized' =&gt; TRUE,
    'getter callback' =&gt; 'MYMODULE_search_agg_gender_getter_callback',
  );
}

/**
 * Getter callback for agg gender property.
 */
function MYMODULE_search_agg_gender_getter_callback($item) {
  // Need to load the user object to get fields
  $account = user_load($item-&gt;uid);
  switch ($account-&gt;field_gender['und'][0]['value']) {
    case 'F':
      return 'f';
      break;
    case 'M':
      return 'm';
      break;
    case 'O':
      return 'fm';
      break;
  }
}