Achh... I tried to get Linux to work with a Speedtouch myself and while many people have had success stories, it just wouldn't work for me. Perhaps I wasn't patient enough.
But eventually, impatience (and 'purism' - I want RJ45 for networking, none of this USB rubbish) won out and I bought a proper ADSL modem
which also functions as a switch for your LAN. The difference was immediate - once I'd set it up with my username and password, it 'just worked'; all I needed to do was declare it as my gateway (and since I was alsready piggybacking off a Windows XP box, this was trivial).
I don't mean to discourage you from getting the Speedtouch working, because even if you fail it's one very educational journey. I merely want to make you aware that's it's not necessarily a quick and easy process, so if you're more bothered about getting something that works, quickly then an ethernet modem may be your best bet. Besides, it's hardly a lot of money, and you can still play about with your Speedtouch once you have a reliable internet connection to look up Google on.