In reply to Chmusar:
I can't speak for the Petit Piton hike, but I found myself in St Lucia last winter, working on a cruise ship. My job for the day was to accompany a busload of our guests on the Gros Piton hike.
I think one in every ten made it to the top. It's a rough, steep track where a slip or trip could have real consequences. Most of them made it to half way.
The 'guiding' thing is a way of creating employment for locals, just give them their few dollars (there is always the upkeep of the trail, handrails etc.) and try to keep up!
I came across one kid, probably 16 or so, who was in a very bad way from heatstroke/dehydration. Fortunately he was a scrawny specimen and we managed to manhandle him back to shade and water. Bring plenty of water and sunscreen and wear a sturdy pair of shoes; approach style shoes or trail runners would be ideal.
If you do it, spare a thought for my colleagues and I, shepherding unsteady 70yo American retirees up and down. We were very late getting back, almost resulting in the ship missing her scheduled departure.