This functionality isn’t available to you in the Zend_Service_Flickr class (as of v 1.11) but you can add this by extending the class yourself and doing something like this:

<?
/**
 * add a method to Zend_Service_Flickr to retrieve lat and lng coords for a given photo id
 *
 * @author Ed van Beinum <e@edvanbeinum.com>
 * @throws Zend_Service_Exception
 *
 */
class Evb_Service_Flickr extends Zend_Service_Flickr {

    /**
     * Return array of lng and lat coordinates for a given photo id
     *
     * @link http://www.flickr.com/services/api/flickr.photos.geo.getLocation.html
     * @author Ed van Beinum <e@edvanbeinum.com>
     * @throws Zend_Service_Exception
     * @param int $id
     * @return array
     */
    public function getImageLocation($id) {
        static $method = 'flickr.photos.geo.getLocation';

        if (empty($id)) {
            /**
             * @see Zend_Service_Exception
             */
            require_once 'Zend/Service/Exception.php';
            throw new Zend_Service_Exception('You must supply a photo ID');
        }

        $options = array(
            'api_key' => $this->apiKey,
            'method' => $method,
            'photo_id' => $id
        );

        $restClient = $this->getRestClient();
        $restClient->getHttpClient()->resetParameters();
        $response = $restClient->restGet('/services/rest/', $options);

        $dom = new DOMDocument();
        $dom->loadXML($response->getBody());
        $xpath = new DOMXPath($dom);
        self::_checkErrors($dom);
        $retval = array();

        foreach($xpath->query('//rsp/photo/location') as $location) {
            $retval['lng'] = (string)  $location->getAttribute('longitude');
            $retval['lat'] = (string)  $location->getAttribute('latitude');
        }
        return $retval;

    }
}

You may want to add some error handling if the picture doesn’t have location data associated with it.