I have just gone through the process of exchanging my U.S. driver's license for a Portuguese one, and I want to describe the experience for others who do the same in the future, but I have a question first for anyone who has done this recently.
The temporary license I received on A4 paper (good for six months; the real wallet-sized plastic license is supposed to arrive in the mail in five months) has a space for a passport size photo marked "Fotografia (colada)", but the clerk didn't put a photo there, and I didn't think to ask about it until after I'd left. Is there supposed to be a photo there? I'm slightly tempted to glue a passport photo there myself, but I suspect that that would just be inviting problems. Does anyone else have a temporary license with a missing photo?
Now for the process. My Título de Residência is dated early August, and the driver's license exchange has to happen within 90 days of that, so I figured I was getting close to the wire and my procrastination had to end. But I see from this very useful webpage: http://maracujaroxo.com/2017/05/10/como-trocar-a-minha-cnh-brasileira-em-portugal/ that it is in fact a question of 90 working days, not 90 elapsed days, so I wasn't procrastinating as much as I thought. But it may not necessarily be easy to convince the clerk at IMT of this - if you're in this situation you may want to bring a copy of the regulation.
Before leaving the U.S., you need to go to the consulate for your region with your driver's license and a copy of your driving record for that license. In the state where I had my license, this could be obtained online in both 'unattested' and 'true and attested' versions; I got the latter and it was mailed to me after a few weeks. The consulate will translate the license and the driving classes it's endorsed for, as well as the details of the driving record, and put them in a signed. stamped, and sealed document that you will need when you get to the IMT in Portugal. You should probably consult your consulate beforehand for details on their exact requirements.
Once in Portugal, you then wait for your Título to arrive. I don't know if you can go to IMT with just the receipt from the SEF Título interview; I suspect not, though.
You will need a medical exam for your Portuguese license. This is a very cursory exam that can be done by any doctor, who will then electronically report the results to the IMT. But for this reporting to happen, you will need a Numero de Utente from a Centro de Saúde, even if you never use the public health service ever again. Not all Centros de Saúde issue numbers, and those that do have limited hours for this - check ahead. You will need Título and passport for this. I see from the web that you might need an Attestado de Residencia from your freguesia, but I didn't. (After all, my address is on my Título.) I went to the Lisbon Alameda Centro de Saúde, where my wait was a mere three hours. I wouldn't be surprised if you could have the exam done by a doctor right there, but with the difficulties of figuring this out, plus the prospect of another three hour wait, I didn't bother, and went instead to a private doctor.
You can now go to a nearby IMT branch (mine was Av. Elias Garcia 103, Lisbon). My wait there was under two hours, which actually was faster than waits I've had in DMVs in the U.S. Give them the translation of the driver's license/driving record, the medical exam report (even though it's been transmitted electronically) and your U.S. license. The clerk had a problem with the fact that U.S. driver's licenses don't list a date of the driver's exam, but we found a date on the driving record which was acceptable to her. After an amazing amount of futzing around in front of the computer screen she gave me an A4 sheet of paper, stamped and signed, that will serve as a temporary license while I wait for my real one to arrive. She then photographed me and said goodbye, keeping my U.S license. The temporary license is good only in Portugal, so I can't drive elsewhere in the EU, or back in the U.S. until I get the real one.