It is my children's father who has bipolar. As an observer of him he is an excellent Dad and even at his worst they are the last for him to break down with(he keeps up a pretty good face with them much longer than with me). If you are stable and commited to a treatment program. If your husband has plans of action to make sure that happens and if not what he would do in that situation then I (with no professional backing only my humble opinion) would allow you to adopt with no problem.
As far as the being pregnant yourself I'd go with the doctors opinion and avoid that. One of the first major occurences of bipolar cycle for my children's father happened just after I had our last child. It was a difficult pregnacy and had me stressed and him stressed dealing with everything. He then left shortly after the baby was born which sent me in to post partum depression. We got back together and I am not dealing with pregnancy hormones this time around when he's doing the same thing. I'm stressed but I'm holding up. The point being that pregnacy messes with you enough to not add another instability to it.