I have shot Provia 400 at 1600 with excellent results. I suspect that it would go another stop without much problem. My exposures were much shorter though. If you have enough time, you can always experiment before you go.
Thanks. Yes...I plan to buy a pack and test before leaving.
Btw...did you use the Fuji specified reciprocity compensation or did you use a "corrected" one to account for the pushed film?