As far as I know a guerrilla is a small scale war, not a person. Or can you call a guerrilla warrior als guerrilla in English?
i think it's more common to say "guerrilla soldier", but people would probably understand you if you just said "guerrilla"
You can just refer to someone as a guerrilla in English. But it's technical language so if out of context, I would use guerrilla soldier to make sure I was understood.