Landmannalaugar is the only accommodation between Hrauneyjar and Holaskjol. The spur road is only about 3 or 4km, but there is a hill to go over. There is a footbridge over the river at Landmannalaugar so you shouldn't have to get your feet wet, but will probably need to demount your luggage and make several crossings to keep your feet dry. The area around Landmannalaugar, for 20km or so, is a reserve with no wild camping - you will see the signs, they put them up long before you even get into the reserve, but they usually have a map somewhere, sometimes on the back, showing you the precise extent of the restriction - it is a lot less than the whole southern highlands. There is also a no camping restriction precisely at Eldgja, though I think if you walk a short distance south down the canyon (flat grassy bottom) so you are not visible from the road, and are on a bike no one could complain. Last time I was in the area, the owner of Holaskjol had put up a lot of home-made no camping signs of no legal force for some distance either side of their facility - you can wild camp in that area so long as you are not within 1km of them, regardless of the home-made signs, the tricky bit is finding somewhere you'd want to wild camp - there's some really nice grassy bits by the river but they are rather exposed to the passing traffic and the wind - we found somewhere with a bit more shelter and privacy a few km beyond H.
