Unfortunately,I don't think you can.
I'm currently on dial-up,as my only option was satellite internet,and the prices coupled with the f.a.p (fair access policy) were ridiculous cost wise.
But getting back to your original question,do you have a friend or family member with internet? is so,all thats needed is a silver account for patches.
Also,IF you do have access (albeit with dialup) you can still get on live to get patches and such....you just obviously won't be able to play anybody.