If I need to repatriate to the US for any reason, can I immediately sign up of the Affordable Care Act or would I need to wait for the "sign up window".

This is a great question and from my research the answer is you would have to wait for the next open enrollment period.

Sign up begins November but coverage begins Jan 2015. The fact we were overseas when the enrollment period was in effect does not appear to make a difference. But please correct me if anyone has verifiable info to the contrary.

I recently read some state exchanges are exploring the possibility of offering a policy mid-term but that it will be priced much higher. The reason being is they want to discourage people from waiting til they are sick or injured to make a claim. And those are only some states exploring that possibility.

There is so much misinformation out there and when I tried to sign up in the last 72 hours, April 13-15, I was constantly denied access to the exchange because, "The site was being improved for my benefit".

Here was some info from last year and its possibly very outdated. It provides a definition of which expats are exempt from participating while overseas.

http://www.bajabound.com/livinginmexico/obamacare.php