FYI for anyone who is interested, what I wound up doing to avoid having to keep my own list is:
var mm = $('#my_menu');
$('.menu-text', mm)
.map(function (i, e) {
return e.textContent
})
.each(function (i, e) {
mm.menu('removeItem', mm.menu('findItem', e).target)
});
Would definitely remove a "clear"/"removeAllItems" method!