The speed limits in Bulgaria 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.
In Bulgaria the motorways A roads, the non motorway main roads are just numbered and the smaller roads just have numbers.
I never rode on the motorways and the non motorway main roads in Bulgaria that I rode on are of a mixed standard, some are good and some can be very bad. The smaller roads were not maintained to the same standard and are generally in a poor state of repair.
The A road motorways signs have a Green background with White numbers, the non motorway main road signs have a Blue background with White numbers, and signs for the smaller roads have a Blue background with White numbers.
Bulgaria does not use the Euro and Petrol at the time of writing it was about the equivalent of 1.20 Euros per litre.
I never saw any signs for speed cameras and I never saw any patrolling police vehicles.
Bulgaria has lots of great biking roads but my favourites are in the South of the country in the area where they go skiing in the winter.
To buy a SIM card for a mobile phone you need to go to a mobile phone supplier 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.