I'm not writing from experience myself but have read many threads regarding touring on larger bikes and I guess this is more applicable to long touring but steel frames, strong wheels and tyres plus derailleur gearing often comes up. A very workhorse approach to cycling to ensure the holiday is more about the holiday than bicycles issues. This is for full size bikes but I'm sure much of it can be applied to folding bikes. Basically you want a bike that either due to a fault, worn part or some sort of minor collision or accident can be easily fixed anywhere by either widely obtainable parts or basic welding skills. I guess it really depends on how developed the country is and how much support is available. You need to look at the bike you are considering with an eye to what could go wrong with it and how would you sort the issue.