Eleanor,
This is one of those questions that only you can answer, I advise some soul searching on the matter, this is a big decision. Some things you should ask yourself are has Joel had open access to Michael? What does he say are his reasons for not being involved? Is he more willing to become involved now that you have mentioned moving? In the end only you can decide the right answer, I agree with the other posters that there is no excuse not to be involved with your childs life but sometimes there are is a rare case where there are circumstances that must be taken into consideration when making such a big decision.
If he is not going to be supportive and involved in his childs life then I agree that a move may be in order.