Can I take my iPhone5 from AT&T to walmart family mobile?

Does the walmart family mobile plans have unlimited data

So much as the phone has a clean ESN, it can be used with Family Mobile.

Wal-Mart Family Mobile bills itself as being "unlimited", but there are throttle limits on the account, that when reached (such as their 2.5GB throttle cap), data speed slows greatly, and there are restrictions on data use as well.