There seem to be quite a few linux compatible usb wireless cards these days! I made a page that shows the results of my testing some of the most powerful cards available for linux, including several alfa cards, and the TL-WN722N. The page is available here:
http://rooftopbazaar.com/wirelesscards/
These cards might be more than you need, but the prices are pretty reasonable so might as well have the best! I trust this will be valuable for you.