A time of frustration

Wow. My 21 month old is REALLY getting to me. He can't talk. He can't understand everything we say, so overall, we are all getting frustrated with him and he with us. Of course it all comes out when we are out to dinner or in public. He is not satisfied with anything and he can't tell us what's going on. Don't get me wrong, he is talking so well for his age, but not in depth and with good understanding. I know it will pass, as it did with my 3 year old, but WOW it's definitely getting old fast.