Buenas, yo lo haría en dos días distintos, por los acantilados se anda bastante y por San Juan, desde donde se dejan los coches a la ermita hay bastante camino y con mucho desnivel.

Hi Helen, we went with our bikes from Vizcaya bridge to a restaurant in Getxo called The Willow, had a really nice lunch there and then cycled to Azkorri. My husband and I are active people so cycling was ok for us, however most of the road was uphill and can get a bit tiresome. I recommend cycling it would take you less travel time and still u get to enjoy the towns you passby. There is also a mini bar on the hill top for refreshments. It took us about an hour and a half from the Willow restaurant. I recommend you check the map and see if you are able to walk the distance. We planned this trip as a day trip from Bilbao and were back in the evening. Hope this helps.