Iceland is typically a great country for hitchhiking, but be extremely careful of the weather in this region, as it is highly unpredictable. As late as March or April, terrible Arctic blizzards can blow in off the sea, and hit you in an instant. If you're even a couple kilometers out of town, and one of these storms hit, you will be stranded for an indefinite amount of time. It's wholly possible to freeze to death, or at least come down with hypothermia or frostbite, in such a situation.
A ferry called Sæfari sails between Dalvík on one hand and Grímsey and Hrísey, operated by Landflutningar (http://www.landflutningar...). Grímsey is only served on Mondays, Wednesdays and Fridays and Hrísey on Tuesdays and Thursdays.
The ring road passes through North Iceland. The stretch of road between Mývatn and Egilsstaðir in East Iceland one of the most remote parts of the road with very few settlements. Because of the shape of the area, many settlements in North Iceland aren't served by the ring road, but road connections are mostly good. Until recently, Siglufjörður was quite cut off, but a tunnel now links it with Ólafsfjörður making connections with Akureyri much better.
Car rentals include Hertz (https://www.hertz.is/?swi...) and Budget (http://budget.is/budgeton...) at Akureyri airport, Bílaleiga Akureyrar (http://www.holdur.is/en/) at Akureyri airport, Tryggvabraut in Akureyri and in Sauðárkrókur and Avis (http://www.avis.is/avison...) at Akureyri airport and in Sauðárkrókur.
Sterna (http://www.sterna.is/en) operates scheduled busses along the western stretch of the Ring Road in North Iceland as well as between Varmahlíð in Skagafjörður and Siglufjörður, and Akureyri and Ólafsfjörður. SBA (http://www.english.sba.is) serves the stretch of the Ring Road from Akureyri to Egilsstaðir in the east, as well as the route between Akureyri and Húsavík and Akureyri, Þórshöfn and Raufarhöfn on the other.