Delete wp_enqueue_script navigation wont work as the navigation were being registered and stored on the database. So for this you need to deregister navigation using the code below:
add_action( 'wp_print_scripts', 'deregister_navscript', 100 );
function deregister_navscript() {
wp_deregister_script( 'twentytwelve-navigation' );
}
This code unregisters the javascript used to toggle the default responsive menu.
Add CSS to hide the default 2012 menu button and to hide the UL menu when the select menu is displayed. Insert the following code in your theme style.css:
/* hide the default responsive menu and menu button */
h3.menu-toggle {display: none}
.main-navigation ul.nav-menu, .main-navigation div.nav-menu > ul {display: none;}