Well one thing that could be contributing to the overall slowness of the operating system (not the slowness of the Internet though) is booting off of a CD. Installing Ubuntu to your hard drive and dual booting will make the operating system significantly faster in general.
I don't really have any good advice on how to improve your connection. For what it's worth though, I can tell you that that I run xubuntu on a laptop with a b/g/n wireless card. My college uses a n-band routers to provide wireless Internet access across campus with b/g as a fallback. It turns out that the linux n-band driver for my wireless card is not very good, and there is a significant speed improvement by disabling n and sticking with g even though n technically has a higher max transfer rate. Use sudo lshw > spec.txt to dump your system specs to a text file, then open it up in gedit to find your wireless adapter. Then look online to see if there's any compatibility issues between linux and your wireless transceiver.
