If your traffic is encrypted and assuming that a proper safe and secure algorithm is used, and the private keys of the server have remained private (i.e the key to unencrypted the traffic) No they could not see the content of your traffic.
I think that you are misunderstanding the terms man in the middle,
it's not like there is someone over hearing a conversation.
lets say that there is you and Alice talking.
you call out to Alice, Alice replies saying I'm here.
you ask Alice something, and Alice replies to you. (that's the normal conversation)
a man in the middle attack is more like.
you call out to Alice but Bob, cleverly disguised as Alice replies. and then bob calls out to Alice.
Alice replies I'm here to Bob, and Bob tell you "Hi I'm Alice"
So then you ask the person that you think is Alice (i.e bob) a question.
and Bob asks Alice, Alice replies to bob, and bob send on that message to you. the whole time you think that you're talking to Alice. but actually you;re talking to bob, who has tricked you into thinking that he is Alice.
if you're asking the weather, probably not a big thing.
if you're doing your on-line banking, that's an issue since a part of that will involve transmission of usernames and passwords, and account details etc.
yes, the ISP knows what site you're connected to, even if they can't see the data because it's encrypted.
