regions.php

<?php $temp_query = $wp_query;

        $args = array(
            'post_type' => 'region' 
        );

        query_posts($args); 
        if (have_posts()) { ?>
            <form>
                <select id="event-region-select" autocomplete="off" onchange='doSubmit();'>
                    <option disabled selected>Select a region</option>
                    <?php while (have_posts()) : the_post();
                        $id = get_the_ID();
                        ?>
                            <option value="<?php the_field('region_slug'); ?>"><?php the_title(); ?></option>  
                        <?php
                    endwhile;
                    wp_reset_query();
                    ?>
                </select>
            </form>
        <?php } else { ?>
            <form>
                <select id="event-region-select" autocomplete="off" onchange='doSubmit();'>
                    <option disabled selected>Select a region</option>
                    <option value="northland">Northland</option>
                    <option value="north-shore-auckland">North Shore - Auckland</option>
                    <option value="auckland">Auckland</option>
                    <option value="waikato">Waikato</option>
                    <option value="bay-of-plenty">Bay of Plenty</option>
                    <option value="hawkes-bay">Hawkes Bay</option>
                    <option value="wellington">Wellington</option>
                    <option value="christchurch">Christchurch</option>
                    <option value="queenstown">Queenstown</option>
                    <option value="sydney">Sydney</option>
                </select>
            </form>
        <?php } ?>