I’m a native Spanish speaker, it depends on the language and the person.

Spanish has very few diacritics, so it’s quite understandable in ASCII (áéíóúüñ). But I guess it would be a lot harder in other languages like Czech or Vietnamese.

When I program for myself or in public repos, I tend to code everything in English, but when I have to do projects with classmates at my university, I usually do it in Spanish because they are not great at English.