Are you using a CMS (like phpWCMS maybe?). I don't know how well Plogger integrates with a site that is already using a $_GET alias at the top (i.e. ?p=gallery) if at all. You may need to just alter the theme / template to look like your site (add the site's "wrapper" content to the header.php and footer.php files). That is all I can think of at the moment.
ETA: I found this discussion on the forum too. Let us know if it works for you! :)
The only other way to integrate it with a CMS $_GET alias is to manually change all of the functions that generate an URL to add the p=gallery part. Can you not just create a separate file named 'gallery.php' or 'fotos.php' and include Plogger the way it is set up to be included?