The speed limits in Slovenia are 50 km/h (31 mph) in built up areas, 90 km/h (56 mph) outside built up areas, 110 km/h (68 mph) on dual carriageways and 130 km/h (81 mph) on motorways.
In Slovenia the motorways are numbered and prefixed with the letter A, the non motorway main roads are numbered, the smaller roads have the name of the place that the road lead to on them.
The Slovenian motorways and the non motorway main roads that I rode on are of a good standard, the condition of the smaller roads are generally good but there is always the odd exception.
Like most countries in the Balkans, the motorways signs have a Green background with White numbers for the motorway number, the non motorway main road signs have a Blue background with White numbers, and signs for the smaller roads have a Yellow background with Black names.
Petrol at the time of writing was about 1.50 Euros per litre.
I never saw any signs speed cameras nor any patrolling police vehicles.
My personal experience of biking in Slovenia is limited to 2 short visits, but most of the roads in the country that I rode on are very scenic.
I did not buy a SIM card for a mobile phone whilst I was in Slovenia so I have no information about how to do this.