The speed limits in Poland are 50 km/h (50 mph) in built up areas, 90 km/h (56 mph) outside built up areas, and 130 km/h (86 mph) on motorways
The motorways are numbered and prefixed with the letter A. Some of the motorways or stretches of a motorway are toll roads but most are not. The main non-motorway roads are also just numbered, and the smaller main roads are also just numbered.
The motorways signs have a Blue background with the number in Red/White, the main road signs have a Green background with the number in Red/White, signs for the smaller roads are also on a Green background but the road number is in Yellow/Black.
The smaller roads are generally in much poorer states of repair than in other European countries, however the other roads are generally good.
There are some speed cameras and there are a lot partolling police cars on the motorways. The police also operate lots of speed traps from patrolling police cars parked at the side of the road on both main and smaller roads.
The Poland does not use the Euro but petrol was generally much cheaper than any country that uses the Euro and at the time of writing was the equivalent of 0.90 Euros per litre.
My favourite Polish roads are those to the South of the country in the Tatra mountain region.
To buy a SIM card for a mobile phone you need to go to a mobile phone service provider shop and you are required to produce your passport to buy the SIM card. When I did this the cost was around 10 Euros for one month of internet.