You shouldcall the Family mobile customer service and ask them about bringing your phone over and any data settings you may need to change. If they want your business, they will try to help you.
Switched my HTC One X to prepaid GoPhone. Unlimited Texting for $25/mo but no Data, Wi-Fi Only. Luckily everywhere you go around town here has Wi-Fi, so it works for me.
If I go out of town though, I tend to get a little bored.
I was thinking of hopping on my fiance's Family Mobile (T-Mobile via Walmart) plan for $35/mo so I can get data access, but I'm not feeling the whole $299 price tag for the highest of the high end phone they have available: Galaxy S2. I read you can use any T-Mobile network phone, but some features may not work properly. It's hard to find information about this... anyone here use Walmart Family Mobile?
I have Consumer Cellular with my N4 and I opt out of data & txt - voice & WiFi is plenty for me, for now. Con. Cell. lists instructions on their website for data settings for GSM phones from other carriers. Maybe Walmart family mobile does the same?