Head out of Cardiff up Rumney Hill. At the top of the hill turn left towards the entrance for teh leisure centre. Take the fourth left into Ball Road and follow that until it drops down the hill. At this point is a turning left, take that (it is signposted as University playing fields I believe). Follow that road it's length and stay on the left, you eventually reach Rumney Rugby Club, where you can park. The playing fields are to your left.

 

The fields are well kept, but wear your boots as there are plenty of dog walkers!!