CakePHP putting quotes around function name in WHERE clause

I'm using various functions from the earthdistance module in PostgreSQL, one of those being ll_to_earth. Given a latitude/longitude combination, I'm trying to retrieve the nearest point from my database via CakePHP 1.2.5 Stable.

// set dummy data
$latitude  =  30.4393696;
$longitude = -97.6200043;

// create a simple bounding box in the WHERE conditions, sort the points by location, and retrieve the nearest point
$location = $this->Location->find('first', array(
    'fields' => array(
        'id',
        'coords',
        "earth_distance(coords, ll_to_earth($latitude, $longitude)) AS distance",
    ),
    'conditions' => array(
        'coords >=' => 'll_to_earth(' . ($latitude - 0.5) . ', ' . ($longitude - 0.5) . ')',
        'coords <=' => 'll_to_earth(' . ($latitude + 0.5) . ', ' . ($longitude + 0.5) . ')',
    ),
    'order' => array('distance ASC'),
));

The SQL output (formatted for the sake of easier reading) ends up looking like this:

SELECT
  "Location"."id" AS "Location__id",
  "Location"."coords" AS "Location__coords",
  earth_distance(coords, ll_to_earth(30.4393696, -97.6200043)) AS distance FROM "locations" AS "Location"
WHERE
  "coords" >= 'll_to_earth(29.9393696, -97.1200043)' AND
  "coords" <= 'll_to_earth(30.9393696, -96.1200043)'
ORDER BY
  "distance" ASC
LIMIT 1

You can see where my problem lies: CakePHP is quoting my find conditions, including the function name ll_to_earth. Will I just need to manually query via the Model's query method, or is there a way to tell Cake that ll_to_earth is a DB function and to not quote it?