McAir, I would like my answer to stick to the statement in your post. Since you're going next week and shooting HP5, you may have little available time for testing, and, as hinted in the comments above, there are more than a few variables -- and we haven't even started with shutters and meters.

Welcome back to LF photography. I returned about four years ago and chose HP5, which was already an old friend, but I switched developer and had to start my testing again.

Black and white, as you may well know, is rather forgiving, and HP5 is a very forgiving B&W film. Naturally, one wants to fine-tune exposure and development, but that's not likely to happen by next week in your case.

Unless your meter or metering, and/or shutter(s) are way out-of whack, I would side with those suggesting either box speed or a stop more exposure (EI 200) for subjects of relatively normal brightness range and normal development. For subjects of low contrast, that will do, but you can also stick to 400 to let the low values fall as they may and give an extra 10-15% development. If you encounter situations of very high brightness range, 200 and perhaps 15% less development will get you in the proverbial ball park. HP5 will offer you elbow room when you go to print; highlights are not likely to block up easily. Enjoy your trip and enjoy your photography. Just take good notes. Perhaps you'll return with some images to share with us!

Have a good time! You fine tune later.