Drive up through the western fjörds, absolutely breathaking!
If you can stay long enough(and if they're open), give the Djupavík Hotel a night or two.*
The southern coast can be beautiful, even if they weathers inclimate. Vík is a great little town, and make sure to hit Jökulsárlón(Iceberg lagoon). Walk around it, take a few hours to explore. Cross the bridge from the main drag where all the tour buses collect, and enjoy the tide moving the big ice chunks around .
Have a fun trip!