Example below takes more than 10 mins to load. Didn't really debug the add_marker function, but I am assuming its trying to resolve the address to lat/long, etc.. which might be causing it to take too much time?
foreach($query as $sale)
{
$marker = array();
$marker['infowindow_content'] = ($sale['client_name'] . ' - ' . $sale['quote_unit_number'] . ' - ' . $sale['item_name'] . ' - ' . $sale['quote_number']);
$marker['position'] = $sale['client_address_1'] . ' ' . $sale['client_city'] . ' ' . $sale['client_state'] . ', ' . $sale['client_zip'];
$this->googlemaps->add_marker($marker);
}