The model number is WUSB54GS
There is no WUSB54GS.
There is a WUSB54G ... Driver and docs available at: http://prism54.org/
and a WUSB54GP v.4 Driver and docs at http://rt2x00.serialmonkey.com/wiki/index.php/Main_Page
Those two cards should work out of the box with Ubuntu, I think. Have you tried poking at the card from Desktop|Administration|Networking? Also look for documentation at the Ubuntu website.
There is also a WUSB54GP-BP which has a Broadcom bcm43xx chipset, and which you probably won't be able to get working right anyway.