No special access issues
The cliff of Seynes lies above the D6 which goes from Alès to Bagnols-sur Cèze. At the village of Seynes, turn of the D6 and follow the parallel track. Park below the sector you want to visit. Approaches are 5-15 min uphill walking.
In the past you could drive onto the track from the West too, but this has been blocked. It is possible to park on the road and walk in.