The speed limits in Hungary 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 Hungary the motorways M roads, the non motorway main roads are just numbered and the smaller roads just have numbers.
The motorways and the non motorway main roads in Hungary that I rode on were of a good standard, however the smaller roads were not maintained to the same standard.
The A road motorways signs have a Blue background, the non motorway main road signs have a Green background, and signs for the smaller roads have a Blue background.
Hungary is in the EU but they do not use the Euro and Petrol at the time of writing it was about the equivalent of 0.90 Euros per litre.
I never saw any signs for speed cameras and I never saw any patrolling police vehicles.
Hungary is a mostly flat country therefore the roads were pretty boring to ride on for me. The only exception was when the road ran alongside a river.
I did not buy a SIM card for a mobile phone whilst I was in Hungary so I have no information about how to do this.