Personally I would go with the Wi-Fi card. You can go more places and get access. Saying modern Wi-Fi card aren't compatible is not entirely true. Actually there is a thread on
listing 802.11g cards that other users have successfully configured. I recently purchased a Belkin card and I use it at college and home (commuter student). I had to use NDISWrapper, but it works. The installation was straightforward and only took about 10 minutes. I even have it running WEP at home.
Bluetooh is an entirely different technology, aimed at short distance communication sans wires. Once you have an adapter you can use all sorts of devices with it, but I would see it as a complement to Wi-Fi not an alternative.
Here are a couple quick Googles on Wi-Fi vs. Bluetooth to help you decide.
Let us know what you decide to do.