How do non-english speaking people code?

I would presume they use a keyboard.

On a more serious note, as a native Finnish-speaker, I've always written all of my code and comments in English. It's just so much simpler than any other alternative I can think of.

If you don't know any English then you don't code. How could you?? Every programmer I know does know some English and can write/speak well enough to be understood.

How does a Spaniard who doesn't know English write French?

About as well as he knows French.

All the Chinese programmers I know can understand some English - especially enough to write code, though many have taken English classes as well. It's possible my selection sample is biased, since the Chinese programmers I know are somehow related to this industry.

FYI: they use keyboards that have both Chinese and English characters on them, like: http://en.wikipedia.org/wiki/Keyboard_layout#Chinese

I doubt it would be that hard. You'd just have to memorize the keywords in the programming language. You don't need to speak English to write code, although it does help.

They would know the meanings for most of the names (classes, functions, operators) even if they don't know English at all.