In reality you need 2 buses, changing in Amalfi and than catching the other one to Bomerano.
Always full in high season and quite unreliable due traffic I see they can be a royal pain.
Last option is taxi but good luck with them. Expensive and hard to find.
The last part of the path (starting from Bomerano) has tons of descending steps (they go on and on at least for half a hour), and no doubt would be more challenging on the way back, therefore I would start in Bomerano, walk until Nocelle, and then get back. This way you'll save the steps part without missing an inch of the view.
So without a doubt the starting point I advise is from the top.