Hi im also new to backtrack, but i did have a good old try at ubuntu last year im running a dell inspirion 1525 that also uses a broadcom wireless card! i had so many problems with it to begin with that in the end i just gave up! In saying that i now believe that some broadcom cards do work! but if this fails have a look at an orinoco gold these can still be picked up at very reasonable prices on the old ebay! Also just make sure it is compatible with your system!
This is just my personal experience and please dont just take my word for it i am certain that others have had the same problems and that someone with more experience and knowledge will be able to shed more light!