I've been traveling Central America now for about for about 40 years with airplanes, cars, trucks and motorcycles. I've carried Blue Cross / Blue Shield for the past 30 years.
I have needed medical attention several times and hospitalized once. General illnesses and one motorcycle accident. Blue Cross always paid their share once I got home and filed a claim with the medical paper work provided by the locals.
I have never heard of a medical facility that will not provide immediate medical treatment to stabilize you. But once that's done you had better have cash available to get admitted to a major facility if you need advanced medicine. Your new found medical insurance, which ever once you settle on is not going to have an office readily available to assume and approve your cost or if the hospital can or cannot do it for you.
South of the boarder medicine does not operate like here in the US.
The biggest problem with a need for medical assistance down south is the time it takes for assistance if you have moving accident. You'll most probably be out in the middle of now where when it happens. Minor medical needs can be taken care of with out too much trouble.
If you have any medical conditions now or take any medication, do this. Make a list of conditions and medicines taken, then write it on a small card (several of them) and put one in your helmet, pockets of jackets, tank bag and in your side cases. You just never know!
Good luck on your trip.