Is it possible to use envy ... without an internet connection?
Did you try?
From envy website
"Envy" is an application for Ubuntu Linux, written in Python and PyGTK which will:
1) detect the model of your graphic card (ATI and Nvidia cards are supported).
However "Manual installation" is also available.
2) download the right version of the proprietary driver for your ATI or Nvidia card from ATI or Nvidia's websites
3) handle the dependencies (compilers, OpenGL, etc.) (according to your OS version and kernel) required to build the module
4) install/uninstall the driver
5) set up your xorg.conf (i.e. the configuration file of the Xserver) for you (according to your system specifications)
6) restart the Xserver for you (if you wish so) (this feature is available only in the textual interface)
... That would be a "no".