You need to change the functioncall that builds the menu in your template.
By default the menu is built by calling show_menu2() with a set of parameters.
(
http://www.websitebaker2.org/media/common/add-ons/README_sm2_en.txt)
<?php
show_menu2(
$aMenu = 0,
$aStart = SM2_ROOT,
$aMaxLevel = SM2_CURR+1,
$aOptions = SM2_TRIM,
$aItemOpen = '[li][a][menu_title]</a>',
$aItemClose = '</li>',
$aMenuOpen = '[ul]',
$aMenuClose = '</ul>',
$aTopItemOpen = false,
$aTopMenuOpen = false
)
the 5th parameter could be changed into:
'[li][a][page_title]</a>'