Some routers let you have an unsecured or lower-security guest network. That's what I did at my parents house. Connected my computer to the WPA2 main network, and the DS to the unsecured network (unless I was buying DSiWare with a credit card - then I connected to WPA2).

Now I have Verizon, and the FiOS routers only support WEP, because, well, screw us, I guess. It's a nonissue, though. If you are on an https:// site, your info being sent is encrypted. Just about any financial site/reputable email client has this security, so they're not going to steal your passwords/bank info/read your emails - though they can check your facebook - that is unsecure..

http://store.nintendo.com/webapp/wcs/stores/servlet/ProductDi...

Doesn't do much good now that it has been discontinued =P If you call around nearby stores that sell used accessories, you should be able to find one. Fortunately, Nintendo offers the software online, so you don't have to worry about it coming with a cd. I used to own the wifi adapter. It worked well. Adding devices was easy and it saved me a lot of money since I didn't have to buy a router. I did end up purchasing one, though, once I bought my PS3. The adapter is probably super cheap, you should consider picking one up!

I will check out my local EB games.