WP Custom Field Filter

<?php
	$params = array('post_type' => 'garimpeiros', 'paged' => $paged);
	
	if (isset($wp_query->query_vars['estado']) && '' != $wp_query->query_vars['estado'] ) : 
		$params['meta_query'] = array(
        	array(
	            'key' => 'estado',
	            'compare' => '=',
	            'value' => $wp_query->query_vars['estado'],
            )
        );
	endif;
	
	$garimpeiras = new WP_Query($params);
	?>
<ul>
	<?php if ( $garimpeiras->have_posts() ) : while ( $garimpeiras->have_posts() ) : $garimpeiras->the_post(); ?>
		<li><?php the_title(); ?></li>
	<?php endwhile; else: ?>
	    <li><?php _e('Sorry, no posts matched your criteria.'); ?></li>
	<?php endif; ?>
</ul>