Visited 26th August 2003: There are two barrows marked on the Ordnance Survey Landranger map. The easiest to see and get to (so long as you don't wear shorts because the heather is dense) is to the east of the A27. The grid reference for this is approximately SC232769, and it's sited on a piece of land with no boundary fence, and apparent open access.
The other barrow is to the west of the road (approximately SC230769), in a fenced off field. From the road it's tricky to make out, and I'm not entirely sure I've photographed the right bump.
Worth stopping off to see if you're passing through, if only for the view out to sea.
The OS map shows both the sites described by Kammer, there is possibly a third mound just 2 metres to the west of the heather covered mound. The SMR describes them all as Dalby Mountain Burial Mound, and then gives them A, B & C suffixes. I prefer to call them Dalby Mountain South West Mounds A & B. The land is owned by the Manx Wildlife Trust and is publically accessible.
On the other photograph, the brown cow does indeed stand in front of the mound, which I call Dalby Mountain (west of road). This is on private land, and was excavated in the past and cremation urns recovered.