The speed limits in Portugal are 50 km/h (50 mph) in built up areas, 90 km/h (56 mph) outside built up areas, and 120 km/h (78 mph) on motorways.
Like Spain, the motorways are the A roads, the main non-motorway roads are the N roads, but in Portugal the smaller main roads are the M roads.
The motorways are all of a high standard but some are toll roads and some are not. Some of the toll motorways are of the automatic type and this means that you need to register your vehicle on the appropriate website before making your journey, however some have manual tolls and you can just pay at the toll booths.
The motorways signs have a Blue background, the N road signs have a Green background, and signs for the smaller roads have a White background.
In Portugal my personal favourites are the N roads, the old main National routes before the motorways were built and if I can, I use these in preference to the motorways.
Petrol is usually about 20 cents per litre more expensive on the motorways than on the other roads and at the time of writing it was about 1.80 Euros per litre.
Portugal has speed cameras however they are generally good enough to warn you of them in advance, so when you see a sign for a speed camera on the road that you are on, generally there will be one within a few kilometres from the sign.
There are many great biking roads in Portugal but in my opinion the best are to be found in the North and West of the country near to the Spanish border.
I did not buy a SIM card for a mobile phone whilst I was in Portugal so I have no information about how to do this.