Like so many others, I spent a couple of fruitless hours with Consumer Cellular, who still "does not support iPad." Unfortunately, Jane's method didn't work for my iPad 2, but I found a way that did, using a standard Consumer Cellular 3-in-1 sim card available from CC or at Target stores.
This may look like a lot of steps, but I've spelled it out in great detail for my 92-yr-old dad in case he needs to do it again. Here's the parent site, if you want to check it out before you update your iPad (or donate to the genius there after it works). http://www.unlockit.co.nz/unlockit/
It took just a couple of minutes, and the cellular data function works perfectly now...
- log into a good wifi network
- navigate to unlockit.co.nz
- at bottom of screen, click on "Create APN"
- Make sure "Country" reads "United States" (already selected when I used it)
- click on "Carrier" and select "Consumer Cellular"
- click "Create APN"
- This will open Settings on iPad. Click "Install"
- Enter your passcode
- Click "Install"
- Click "Done"