Mbala is the ruins on top of the cliff where Nany Pupu lives.
Edit to add: It's somewhere between 20 and 30 days travel no matter *how* you go. The main difference is difficulty.
The ocean voyage from Port Nyanzaru is probably the fastest, and the least work for you, if you can get a boat down the Soshenstar River. With a boat, it's six to ten days. Without, twice that. The Brazen Pegasus, I think it was called, is a fast ship (it goes a hex in an HOUR in good conditions). So it might be worth it, even if it's a tough slog back down the river.
...Assuming the 'Pegasus can be found in Port Nyanzaru as expected.
OTOH, You can check out the Heart and/or the Shipwreck, going the other way. You can speed *that* trip up with a boat as well, crossing the Aldani Basin at 2 hexes a day (or so) but of course, you need a boat.
Sorry about the boat thing. They really wanted your canoe for the sick.