I have an international medical insurance policy that follows me anywhere in the world that I use for emergencies. I pay out of pocket for everything else because the costs are usually so much lower.
You can't use your Medicare outside the US because Medicare will not pay any healthcare facility that's not in the US. What some people do (because it’s relatively inexpensive) is to maintain Medicare part A in the US if they ever need to use it so they can always come back to the US.
It's important to be covered anywhere you are. Any type of basic insurance you can have when you're in US is definitely ideal to have. I have never had a problem. I always had good experiences with medical facilities in different countries. I injured myself once in Czech Republic. No one spoke English in the hospital but the care was good and it all worked out and I got my insurance to cover it.
I've been to medical facilities and hospitals in Mexico, Nicaragua, Costa Rica, Canada, Thailand, Australia, and probably a few other places. If you don't have anything that's an expensive, ongoing serious condition, you’re in overall good health and you just need to go for a checkup, it's generally pretty affordable to pay out of pocket. My insurance has a multi-country travel and medical insurance option. It’s only US $300 to $400 a year. It includes my baggage, emergencies like life flighting, death or dismemberment.
I ended up having to go to the emergency room in Costa Rica twice in a week. I had to get an IV and it cost around $1,000. In the end, because I had to get so many things done in two different days I had my insurance cover it. If I just wanted to go to a normal checkup, it would cost way less. A dental cleaning can be $20 -$50 in most places outside of the US. I was in North Carolina recently and was told that it would cost $500 for a dental cleaning. When you’re overseas, you can definitely pay out-of-pocket for anything like that.
When I was in Nicaragua I had an ear infection, so I went to the public clinic. I had to pay for my prescription for my infection. However, the actual cost of going to the clinic (and they gave an itemized receipt), was the equivalent price in US dollars of around one penny. I was there for a couple of hours. Pretty much anything that you need to get done, even if you go to the hospital when you need to see a doctor for something specific, is not usually not going be more than $40 or $50. It's usually cheaper to pay out-of-pocket and you can go to a private doctor, a private hospital, or a private clinic in places like Panama, compared to paying for some really expensive insurance that's going to cost more than going to the doctor, anyway.
(Kristin Wilson, traveling for The World Series of Poker, pictured.)