I also used the sunflower book. walked for 2 weeks using local transport. If you organise according to bus time, you can fill 2 weeks walking every day. Buses are very reliable. I could flag down the bus between the bus stops when I went (some years ago). I only took one organised tour where I couldn't go with public transport. Levada walks are mostly flat as they follow the water. The most difficult bit was to go down sometimes steep hill to catch a bus at the end of the walk. Also, as I stayed on the hill in Funchal, it was hard work to get down to bus station in the morning. Why do I not remember going up hill to reach the leavada being hard work???
Generally speaking, I like going up hills, hate going down. Maybe that's why.
Don't forget to take your touch. Some levadas go through tunnels, which are not lit and the ground is uneven, mostly no rail between the water and the path.
I really loved the green and pleasant land with full of wild flowers. Man made gardens were beautiful too. It was a tropic paradise