Drupal is awesome, but without clean URLs it can make site configuration and menu setup exceedingly annoying.
In the newer versions of Ubuntu, the Apache config has changed just enough to make me re-do a bunch of stuff when setting up a new Drupal install. Here is the way I was able to enable Clean URLs from a base Ubuntu 14.04 LTS LAMP install:
# a2enmod rewrite
# nano /etc/apache2/sites-available/000-default.conf
Add just under DocumentRoot /var/www/html
Allow from all
# ls /var/www/html/.htaccess
If nothing shows after using the above command, download Drupal again and copy the .htaccess file to that directory