ATC at International airports (ones with Customs) is supposed to speak English.
It is only if you rely on the Schengen concession, or do non-border-crossing flights, that you can end up at airports where ATC genuinely does not speak English, and then you have to know enough of the local language to get by.
That's the choice you make in aviation... same as you make when you go to Country X for a holiday and walk into a shop and ask for 3 bananas
Worth a mention that even if ATC speaks English, there is NO obligation for any ground workers to do so and this can sometimes result in "interesting" situations
I recall phoning up Pamplona re avgas availability and after spelling alpha victor golf alpha sierra about 5 times I gave up and flew elsewhere.
Regarding working out which airports can be used, basically it comes down to Schengen or non-Sch, and of non- then you need Customs.
This is quite a good free site for airport data. Personally, I contact every foreign airport I fly to, unless it is a known well organised H24 one e.g. Prague.
I have some notes on this - sent.