Yes - the assumption is that there is some network connection present. One assumes the existance of some kind of internet connection if you are downloading tarballs of ndiswrapper sourcecode.
Personally I use a wired connection at an internet cafe for this. You have
an ethernet card, right? (It is worth it because you can do a complete system overhaul on them if you get the right cafe.)
Other options include, using someone elses ubuntu computer to download the debs for you (or even as a temporary proxy). You can also seek out the deb files in the repo site and manually install them with dpkg if you don't have access to another ubuntu computer. And, of course, you can dig out that old serial modem as a temporary stopgap