The hike down to the Llanos de Cortes Waterfall from the parking area is about 10 minutes and it is a little tricky. Here is a post (Llanos de Cortes) we did about it which also has a picture of the trail. There are some large rocks and some roots but maybe with a little assistance your family member can make it down?? Enjoy!
Answer for How far of a hike is it to Llanos de Cortes from parking the car?