1. It's never been stated anywhere that we can read foreign languages thanks to the Echo. Since the Echo basically works by auto-translating spoken words, I don't think it applies to text. Could be wrong, but until we get clarification on that detail (if ever), I have to assume that text translation is not a feature of the Echo package.
2. Since the Echo auto-translates any spoken words, whether or not it allows us to speak other languages is a bit redundant in regards to the Ascians. (We might not be able to imitate their black speech, but since they also have the Echo they understand what we're saying anyway.) I don't think it does, but until a situation comes up where that could be an issue, I don't think we'll get an official explanation. With enough exposure the Warrior of Light could probably imitate any language, but...