The British are notoriously bad when it comes to learning another language, there are exceptions obviously, but I am not one of them, I have enough of a problem with English never mind Portuguese, bearing in mind I spent over 2 years in Brasil you would think I should be fluent by now, but that was 15 years ago and my memory is bad, what was I saying ?
Anyway fear not any expat can get away with pointing, make pig noises, or clucking to get what you want, just kidding but I do know someone that made piggy noises to ask for a shoulder of pork while tapping her husband on the shoulder, funny thing was the butcher she was making the noises at spoke English as do a lot of people in Portugal, even on the Silver coast away from the main touristy areas.
Going to a Doctor, clinic, pharmacy, or Hospital should hold no fear as I have always found a member of staff able and willing to speak English.
Most of the larger shopping centers have stores where nearly every one of them has an English speaker, you’ll be lucky to leave a store with your credit card undamaged.
That said the Portuguese appreciate it when foreigners at least attempt to converse in Portuguese and there are plenty of schools around and along the Silver coast that teach Basic to advanced Portuguese, prices vary but as a guide they start around 75 Euros a month, away from the schools there are private tutors who charge around 10-15 Euros per hour depending on the level.
Do not let the fact you cannot speak the language put you off coming to Portugal, the Portuguese are very very friendly and forgiving of us expats coming to settle in their country and welcome the diversity we bring, one thing I would say is please do not immerse yourself solely in the expat community, if you want to learn about the real Portugal, mix with the locals, get involved with your neighbors organizing a fair or fiesta, they really appreciate your help and you will quickly make amigos and even amigas.