Anyone try using the eDGe with a MyFi device?

If so, I have a couple questions that may be a bit off topic for this forum.

1. If I have an AT&T phone already with a data plan, can I get a MyFi via third party that I can just pop my SIM into instead of paying for another data plan?

2. Does the MyFi use Ad Hoc or Infrastructure Wireless? If Ad Hoc, then we are dead in the water as the eDGe does not currently support Ad Hoc

Thanks

Craig