Visited twice and well worth it!
It's only a few hundred meters from when the Camino exits onto the road. Rather than turn left and follow the Camono, cross the road and walk straight. You'll see a small kids park on your left and just keep walking. Very easy to find but not well marked.
My first visit a fellow pilgram suggested we go and I didn't even feel like investing the few hundred meters but was very glad I did. Thus the second time visit.
It's free and you can put your pack down and walk in the shallow pond at the base of the falls. There are bathrooms and plenty of area for a picnic. There is a small cafe there to built into what was once a mill I think if you want a meal.
I was there in the fall and spring and both times the water was very cold and refreshing.
Also there were few or no pilgrams there, just locals and a few local Spanish tourists.