lol this is gotta be a first someone asking help for a porn site, but the query you would want is something like this
echo"<select name=username>";
$conn = mysql_connect(connection stuff here);
mysql_select_db(dbname);
$query = "SELECT escorts FROM tablename WHERE location = '$location_selected'";
$result = mysql_query($query);
while($r=mysql_fetch_array($result)){
echo"<option value=\"$r[escorts]\">$r[escorts]</option>";
}
echo "</select>";
mysql_close($conn);
?>
hope this helps