Jeronimo and his wife provided the BEST overall stay we've had with Airbnb. They were incredibly communicative, so much so, that they checked in on us (via text) from time to time just to make sure we were okay and to ask if we needed anything.
Their place is very central and walking distance to everything. The nice thing about their place is that even though it's very central, it's tucked away enough that you aren't in the middle of all the hustle and bustle.
In terms of their actual Airbnb, it was clean, organized, comfortable, had everything we needed (washer, stove, refrigerator, kitchen with dishes, iron with ironing board etc). The shower was a bit small but it served its purpose.
There is plenty of parking on the street below, in case you have a car.
We highly recommend this space because it will give you everything you need for your stay in Porto, but more than that, Jeronimo and his wife are everything that airbnb is meant to be. They even greeted us and sent us off with ice cold water bottles and yummy homemade cake.