I understand that you have to activate the game on Steam with the CD-Key (Already done that), but do you have to have an active internet connection for the entire ~24gb install or can you install from physical discs after activating the game on Steam? If so.. How do I?

I travel for work and never have a reliable internet connection other than tethering my 4g phone to my laptop, but 24gb worth of downloading is going to [censored] my phone bill.. I already pay $200/mo for 15gb worth of data!

Download, there is only the one DVD and it doesn't contain any of that 24 gb of data ya need to install.

Unfortunately you have to down load a large portion of the game files. I would suggest if you are staying in a Hotel to use their Internet to do the download rather than your mobile device.