I'm n00b so don't take my word for gospel. But I believe I read some where that when using VMware you don't need to install drivers on the guest OS because (in theory), they are installed and working on the host system. The host system dishes every thing out to the VMware, and thus the guest OS more or less automatically. Are things not working that way for you? I also believe that in order to get WiFi working in backtrack5 there is some initialization script you have to run after boot. But once again, I am a supper n00b just like you so you will need confirmation by a pro member before you try any thing.
I actually have a RTL8187 based USB dongle around here some where. I don't use it because I get unacceptable packet loss with any x64 OS. That might be your problem, bad support by the host OS. When I get the time I'll look for my dongle and give it a test and see what happens on my end.
I Hope that I was helpful.