How to get to Kerlingarfjöll
It says on the Kerlingarfjöll website that it's accessible for all cars during the summertime. I was sceptical about that. Some roads in the Highlands of Iceland are very rough so I decided to drive to Geysir and take the bus from there. I usually have fait in my tiny Kia Picanto, but this time I decided to play it safe.
If you have a decent car, preferably a jeep, you can drive all the way to Kerlingarfjöll when the roads are open during the summertime. Information about road conditions in the whole country can be found here. This PDF is also great if you want to have an overview over all roads in Icelands, for instance which roads are paved and which aren't.
It's also possible to traverl by bus, either from Reykjavik or Akureyri. If you take the bust from Reykjavik, it will stop far a half and hour at both Gullfoss Waterfall and Geyser - two of Iceland's most famous attractions. i was thrilled that I got the opportunity to see these beautiful spots, I hadn't been there since I was a child.
If you have a tiny rental car, it's possible to do what I did: Drive to Geysir and take the bus from there. you can buy bus tickets here. I also highly recommend the Reykjavik Excursions Highland Circle passport, if you will be traveling some more in the Highlands.