OK - Monte Cristo and "healthy" do not belong in the same sentence. I personally wouldn't trust the macros on that. I used to work in a restaurant and if you don't make them 100% correct then they flood with grease and the calories change significantly. Having done BB competitions etc - I can totally relate to MyFitnessPal and counting macros.
So here is my advise - if you are normally very good about what you eat and you want to enjoy the sandwich - GET IT. Eat it slowly and don't feel compelled to finish the whole thing - if you do though. That is ok.
You will be walking a lot more than normal. Just try to eat more balanced for the rest of your trip - but if you want this indulgence - get it and enjoy it.