Hi,
Born in Spain, on the northern part of the Portugal border, but I live in Florida (dual citizenship). Due to family reasons I have been living between USA and Pontevedra, Spain ( about 30 miles/50 km from Portuguese border). Since I am exposed to both living system, I'll give you my opinion:
1) Be prepared to a different weather pattern. The Atlantic east coast is humid and windy. When you look at the daily temperature charts, they look average mild, but it can be uncomfortable due to the wind and rain. The coast of Portugal, and Spain, do not get any snow, but it get plenty of rain and wind. The south , close to faro, is more influenced by the Mediterranean/ weather pattern than the north.
2) European cities are very nice, with everything close and always something is going on. But with all the tourism, students and party going on, several parts of the cities have noise up to 5-6AM several days of the week.
3) Portugal was very friendly to expats (also called immigrants) willing to meet some means scale when buying a house of having a job with a specific income. That generated waves of gentrification with the locals being priced out of renting and buying houses in many parts of the country. There is a discontent going on the country and some of the visas and permits are going to be eliminated soon. Similar situations are happening all around Europe.
4) Be prepared for a bureaucratic culture shot. I cannot decide If I want to retire in the USA or in Europe due to the bureaucratic nightmare. Yes, that bad. The longer you live in the country, the worse it gets. Having someone one to guide you and help you with this is a must.
5) If you decide to live in a city, choose the area carefully. Some areas have become "theme parks" dedicated to tourism.
For the rest Portugal is a nice modern country with very low cost of living compared to the States. Portuguese people tend to be nice and tolerant and crime is low, in my experience. Two nice airports to travel anywhere. Train out of Portugal is not the best as the connections with the rest of Europe are still being developed. In a way is like living in south Florida, you are at the edge of the continent.