The tsunami of September 2018 thoroughly devastated many parts of Palu, and non-essential travel to Palu is not recommended.
There aren't too many activities to keep you busy here, but there are trekking options from Palu to Lore Lindu, Bada Valley, Dumoga Bone and Halmahera Maluku to name a few. English guides in this town are very hard to come by, Indonesian speaking guides are easy enough but it takes a lot of the fun out of the trek when you don't understand a word the guide is telling you. I managed to find one English speaking guide who took us on a four day hike through Lore Lindu. It was a fairly simple route but I think he can tailor make hikes if you have any preferences. His name is Adri and his email address is [email protected]