Will facetime ring on both devices?

I've already got an ipad 2 and i'm getting an iphone soon but was wondering if someone calls me on facetime will it ring on both devices?

It does if the email address you setup on both is configured the same, I had a friend call facetime via my email address and it called on both devices, you can only connect 1.

Yes it will depending on how it is configured. You need to go into Settings > Facetime and select Receive Facetime at the email address/phone number associated with those devices.