Grab posts by multiple categories

You should be able to use this:

        if (isset($meta_field['category'])) {
            // Get all post data for that category
            $post_data = get_posts_by_category($meta_field['category'], 0,
                $post_limit);
        } else {
            $args = array(
              'numberposts' => $post_limit,
              'offset'=> 1,
              'category' => '9,3',
            );
            $post_data = get_posts($args);
        }