Yeah the roads are not meant for fast driving, there are some rather hairy turns, twists, drops, its best to keep around the speed limit. The roads here are very unforgiving, if you end up going off the road you don't end up in grass but lava rocks.
Also a good tip is that by law speed cameras HAVE to have a sign about 1 km before you drive by them to warn you of their location
Look for this sign:
If you keep an eye out, like Icelanders do you never get fined, not to mention we know where they all are, so sadly its just foreigners that get dinged.
This is what they look like:
