I just installed 9.10 on a brand new Dell Vostro 1520. The WLAN card does NOT work out of the box. Here is what you have to do.
After install and rebooting insert the live CD
go to software sources (system > software sources)and check the "officially supported restricted copyright" box
you are then asked to update the available software list, do so.
You will receive an error message since you are not (yet) connected to the internet and all the other repositories are not available.
Now you should be notified that restricted drivers are available, if not you can go to system > hardware. Anyway, now you should be able to activate the Broadcom STA driver.
After rebooting you can connect to available wireless networks.
Alternative (in case you are not asked, which happened to me on another Vostro system) system>administration>syaptic package manager
search for broadcom
mark b43-fwcutter and bcmwl-kernel-sources for installation
reboot (who said there is no rebooting required in linux)
the adapter should be up and running