1/3-stop bracketing on C41 is pointless, you'll not tell them apart except by looking at the edge numbering. Shoot at box speed or half if you want the extra shadow detail; don't bother doing both because the film has enough latitude that you'll struggle to differentiate even the one-stop brackets except for a little change in shadow details. Highlights will look a teensy bit better at box speed as there's a gentle contrast rolloff with overexposure.
Originally Posted by DanielStone
The film captures way more dynamic range than you can print. Use the same mindset as when shooting chromes and for setting expectations as to how much dynamic range you can fit in the scene and you won't be disappointed.
And absolutely I agree you don't take an unfamiliar film on a once-in-a-lifetime trip. You need to know how it will respond before you open the shutter.