The real problem is not with national coverage of ADSL/3G, the problem is with broken terrain and loss of line of site. ADSL signals are only generally good for 4 to 5km from the nearest equipped sub-exchange. In the Vila de Bispo area, this means Vila de Bispo / Raposeira. As phone lines do not always run as "the fly crows", there can be situations where a property may be phyiscally closer than 5km to the sub-exchange but because the line runs around the houses the phone line longer.
As regards 3G, the problem is that there has to be an unbroken line of sight for the signal to follow between the dongle and the 3G Mobile mast. This has become a major problem for many people living in the country. I have friends near Bensafrim who bought a house in a valley. I ran 3G tests there. At the top of a 30m rise behind their house there was a good 3G signal but further down in the house none.
One possibility is to mount the 3g unit on one's property where there is a good signal, order a 3G booster antenna, and then run a wireless/or wired lan network signal to the computer.
The moral of the story is that if you are going to buy a house in Portugal and require Internet, check the net availability yet.