Best way would be to do an ADB push:
adb push update.zip /sdcard-ext/
That, or put your phone into USB mode and then copy it to the external sd card.
ADB PUSH is the way I would go.
On another note, I know we can't go back to GB after this. But, if I end up bricking my phone for some reason after going to ICS, how do I get it back to being operational or do we have to wait until an ICS fastboot image becomes available?
For now, If you screw something up or get a bad ROM flash with bootstrap, you can just use option #2 to re-install the .211 update. Since this will be the Official OTA, eventually we'll most likely get the .fxz file to restore through RSD or fastboot.