American looking at Masters Programs in Porto

Hi and welcome to the forum.

Whilst waiting for others to reply try www.numbeo.com for living costs.

Have you checked out universities for course costs.

Hello.

I congratulate you on your sense of adventure.  But some more info is needed :

1]  What degree are you reading for at the moment at Tulane ?

2]  You say you 'know' Portuguese but at what level ?  Are your parents Portuguese origin and do you speak Portuguese at home ?
This is an important detail ( the extent of your knowledge of Portuguese, especially as you say you have never visited Portugal ) as unless you are really truly absolutely fluent in Portuguese you will have great difficulty following lectures / seminars in that language.

3]  Is there some particular reason you have decided upon Porto ?   It is a good university,  by reputation, and certainly an interesting city to live in, but there are other University options which might be cheaper  ~ eg Évora, smaller, very beautiful,  probably an 'easier' place for a foreigner to integrate with other students in.   
You need to check out the websites of the various possible Universities  ~  these are extensive, I know, both for Évora and Porto, and probably other places as well.   Just search online and the sites will come up.

4]  What is important above all is to find a course which is well taught and which you would enjoy, ( this comes back to your knowledge of Portuguese ) and which would advance your career.   .......... If you can find such a course in a 'liveable' city, such as Évora or Braga, I would suggest  think about there rather than a big city such as Porto which will be correspondingly more expensive.

5]  There is no doubt that the course fees  [ 'propina' in Portuguese ] will be a lot cheaper than in the States.  Also the cost of living.  The Universities usually post their Propinas on their websites  ~ but be sure to check the price for non ~EU students : it is usually more than for EU students,  but still  a lot  lot less than in the USA.

Please answer the above and then ask more detailed questions, when you have investigated the Univ websites and maybe found a post grad course which attracts you.