I don't yet have residency beacuse I am here from the US as a tourist but I need to see a doctor for a health problem. How do I do this? Will it be very expensive?
You could go to the local Centro de Saude and wait to be seen. I doubt the charges will be expensive, if the doctor will see you. The other option is to go to the emergency center at the nearest public hospital. I had to do this when I first arrived thanks to kidney stones. I was seen, treated and had an ultrasound for less than 50 Euros.