Jessica -
As someone who does have access to the GM, this was one of the first things I was looking to do; Although there was a "Customize" option in the installer for the GM, I was unable to select it - and as a result found no direct way to remove language packs; In addition, one of my favorite tools under Leopard & SL [MonoLingual] did not seem to work properly under Lion.
I will however say, that I am impressed by the size footprint of Lion when a clean install is done. The footprint was about 5.75 GB for the default install; This number does not however include the size of the sleepimage that will be created by the installer. This sleepimage is related directly to the amount of RAM that your machine has. So for my 8GB MBP, the TOTAL footprint was ~ 9.75GB and for my 8GB 17in MBP, it is ~ 14GB.
John