Hi, I would say that all the medical teams aboard all ships will be excellent. They all will speak English, I have never come accross a medical team that can't. Most often than not there are a great deal of English Doctors and Nurses aboard the ships, especially aboard the Princess, P&O and Celebrity Cruise Lines that I have travelled on.
Most of the ships we have used have had extremely good facilties and all the staff are very fluent in a number of languages. I must admist this would not be something I would have had as a priority, but possibly one or other of you are perhaps not in the best of health. In my case few years ago a brain tumour and my wife a stroke, but this has never put us off just make sure you check with your insurer they will you have the cover, we found out a neither of us had any real problems in the past 5+ years it was not a problem. You can also obtain your medical card which helps out in nearly all the European ports, your GP should be able to help you with this. If you do need to use the medical facilities on most ships it is not free so keep your receipts to claim back from your insurnce company when you get back home.