Don't Install It If You're Traveling
If you're about to take a trip (for business or pleasure) or if you're in the midst of a trip, you should think about installing the update upon your return.
You don't want to be dealing with Marshmallow problems (camera issues, issue with GPS, etc) on a trip with your family or on an important business trip.
If you're planning to return soon, we recommend waiting until you're back at home base. You'll be in a much better place to handle any Android 6.0 problems that emerge after you install the update. You'll also be able to devote more time to learning about Marshmallow and all of its changes.