Navigation links in a region rendering vertically
You can copy the responsible template file from bootstrap theme and put it in sub theme. I think you will find your template under Menu folder in tempaltes of bootstrap theme (parent theme)
You will find these files and you have to modify one of these in order to achieve what you said.


menu-link.func.php
menu-local-action.func.php
menu-local-task.func.php
menu-local-tasks.func.php
menu-tree.func.php


Thanks