I want to retire to Portugal :) It looks as if I never will be able to retire, as it goes, but I still go fantasy house shopping on a regular basis!
Brits often equate "Portugal" with the Algarve, which is totally daft it you look at a map. My location of choice would be Nazaré, on the Northern coast. It's a wonderful old fishing port and has been targeted for regeneration funds. It still has the old town, with houses that are built on a Moorish-type courtyard model. I love them. Nazaré is easily reached from Lisbon or Oporto, and is on major roads & railway. It has one of those beaches with a very wide fall - almost a km at low tide. It is a surfing centre. Figuera da Foz is lovely, too.
There are loads of other enchanting towns along that stretch, including the walled mediaeval city Coimbra - it's really lively and historically gorgeous, and was cheap last time I looked.
Seaside resorts outside of Lisbon are still cheap for property, and gaining popularity with ex-pat Brits. Lisbon itself, and Oporto, are both fun places to live (Lisbon if you're an arty type.) The Douro valley is breathakingly beautiful, has good road & rail service, and laughably cheap compared to somewhere like the Loire.
The region over to the East, called Trà s-os-Montes, is the most untouched, "real", rural Portugal and land is ridiculously cheap there. Road & rail services are still weak, however, which is why it's remained stuck in the past. Ime, you can still be frozen out around there for not being traditionally Portuguese. I've met some English couples who settled there for farming, and made a good success of it, but it wouldn't be my recommendation for an easy retirement.
The Algarve climate is completely different from the rest of Portugal. North of the Monchique, it's cooler and wetter although still much milder than the UK. I believe you can still find affordable fincas for renovation in the Serra de Monchique, which can give you the best of all worlds as long as you're okay with driving on rough mountain roads and organising renovations. Quite a few low-profile expat millionaires have done so.
Portuguese food is big on fish and pork. In the towns, now, you also find Brazilian churrascerias with barbecued meats to die for.