The lower town and beach are walkable from the station. Getting up to Haut-de-Cagnes from the lower town requires either a steep uphill walk of about 20 minutes, a taxi, or a local bus — the gradient is real and in summer heat it is worth taking the bus.
Once you are in the upper village, everything is on foot; Haut-de-Cagnes is entirely pedestrian, the lanes too narrow for cars. The Château is at the very top. The Musée Renoir (Les Collettes) is on the edge of town between the lower and upper parts, a 15-minute walk from the Château — downhill from the village, easy to combine.