If you speak English and another language - I would go with the most competent agent first. The one who will work hardest to get you the best deal (whether listing or buying.) If you find two equally good agents and one speaks both languages - I don't see why not.
Sure. My only question is whether they're fluent in my language (if the transaction is between various parties all speaking the same language I do). If I'm dealing with a buyer or seller whose native language isn't the same as mine, I'd want the Realtor to be fully fluent in both languages.