Why would they have a service with a 5 GB limit if they have another one that is cheaper?
Who knows, 6 months ago when I upgraded my phone the prices were the other way around.
You will half to buy a phone and sign a 2 year contract. A laptop card wont be to useful since the only plan has a 5GB limit. Another plus with a phone is you can have your internet with you all the time, in one compact device. I would recommend a phone with Windows Mobile on it if your not going to get voice services. Skype has a program for WM but ive never tried it. The refurbished version of my phone is down to $109, but I would recommend getting a smart phone before you go right to a Pocket PC.