Good luck with your trip! (I spent the summer of 2013 in a boot, and then non-weightbearing after they figured out it wasn't a sprain, but broken, and then in a boot again during PT - literally the whole summer from 6/1 through Labor Day.) But the saving grace was that, with the boot, I could pretty much walk normally. I mean, it didn't get better, but didn't get worse or hurt more from my walking in the boot - they are pretty amazing. I went pretty much everywhere with it. When I was at home (or the office) and able to put my foot up, I did. Ice worked better for me, to keep the swelling down, but everyone is different on heat/cold thing. You should have some ability to do this during down time (even if it is in a bus, sitting at a cafe or on the deck of the boat with an adult beverage). And yes to a supply of Advil.
And I echo the comment about Europe not being as accessible friendly as the US - all those cobblestone streets, fewer hand rails on stairs, etc. Be careful walking around. I find that I spend so much time looking down to not trip when I'm in Europe, but I so want to be looking up and around at all there is to see.
Oh - one other point - try to find shoes that are the same height as your boot, so that you aren't walking all odd (like one leg is shorter than the other). For instance, I had two pairs of heals that worked great with my boot, and so did my tennis shoes, but no sandals or flats did.
Again - hope you still have a wonderful trip!