Then set GRUB_TIMEOUT to whatever value (in seconds) you like more. 0 is acceptable. Use
sudo nano /etc/default/grub
for a manual page. Afterwards runFor comparison, these are the uncommented lines of my /etc/default/grub, which is the default for non-dual booting systems. Using these settings the menu won't display.
info -f grub -n 'Simple configuration'
To be able to boot windows easely, I suggest you set a timeout of about 3 seconds. Waiting 3 seconds during boot shouldn't be much of a problem.
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`