Include plugin´s table in custom query

This was the solution:

<?php
/**
 * @package WordPress
 * @subpackage U-Design
 */
if (!defined('ABSPATH')) exit; // Exit if accessed directly
get_header();
include('scripts/search_excerpt/ylsy_search_excerpt.php');
$search = $_GET['s'];
$all_users = new WP_User_Query(
array(
    'role' => 'dc_vendor',
    'meta_query' => array(
        'relation' => 'OR',
        array(
            'key' => '_vendor_country',
            'value' => $search,
            'compare' => '='
        ),
    )
)
);
//echo '<pre>';
//print_r($all_users);
//echo '</pre>';
?>
    <div id="content-container" class="container_24">
        <div id="main-content" class="grid_24">
            <div class="main-content-padding">
                <?php udesign_main_content_top(is_front_page()); ?>
                <?php
                if ( ! empty( $all_users->results ) ) {
                    foreach ( $all_users->results as $user ) {
                        echo '<p><a 
href="http://www.example.com/vendor/'.$user->user_nicename.'">' . $user->display_name . '</a></p>';
                    }
                } else {
                    echo 'No users found.';
                }
                wp_reset_query(); ?>
                <div class="clear"></div>
                <?php udesign_main_content_bottom(); ?>
            </div><!-- end main-content-padding -->
        </div><!-- end main-content -->
    </div><!-- end content-container -->
    <div class="clear"></div>
<?php
   get_footer();

No need to JOIN the usermeta table.