If you are in an English-speaking country then one of the two language options will be English. Not a lot of demand for bilingual without English in such countries. In Canada, where there are two official languages, the bilingual option will be English and French. In the US, I would expect Spanish to be the second language. But of itself, "bilingual" does not say which two languages are available, just that there are 2 languages, so caution is appropriate. I would be seriously ticked off if I purchased a bilingual item (like a video game or movie, say) in North America and one of the languages was not English.