Originally Posted by stoat
I don't know about broadcom-wl and USB devices. Maybe BlueC (aka Chris) will come by here.
And here I am!
TBH, I'm not actually sure whether broadcom-wl works with USB devices (the docs don't explicitly mention it), but I can only assume that the driver mentioned in Ubuntu Restricted Drivers by the OP is in fact broadcom-wl (proper name: wl-kmod) because AFAIK there are no other USB compatible broadcom wireless drivers in Ubuntu Restricted Drivers.
So, I would say to give it a try and let us know whether it works. The instructions are here: