It is no problem to go around Iceland in three days.
When I do it I usually sleep in guesthouses with bed and breakfast.
I recommend Hotel Edda That is a cheap chain of hotels that can be found all around the circle road.
Bring your own sleeping bag and ask for sleeping-bag accommodation. That is that cheapest way to go. In some cases they will give you a made up bed for the price of a sleeping bag room due to the fact that they use the same rooms for normal and sleepingbag guests. the price per night is around 40-60$ Breakfast there is cheap too maybe 10-20$
There are plenty of gas stations around so you will find one at least every 150 miles or so.
If you do a google search you can find lots of different accommodation all around Iceland
Hope this helps
|