11月の前半の土日は空いてますか？って英語でなんて言うの？

When you ask someone what a particular weekend 'looks like' for them, you are asking if they have any pre arrange plans already or not?
If you ask someone if they are 'around' at a certain time this is the same as asking them if they're free or not. This can be used in any time context, for example - "Are you around in a couple of hours?" or "are you around tomorrow evening?"

We can use a number of different ways to see if someone is free. Usually we would say "What are your plans..." or "what are you up to...". We can also ask "Are you available" they all mean the same thing. If you want to ask if someone is available on a weekend in the first half of November you can say "On weekends in the first half of November" or "In the first two weekends of November"

If you want to catch up with someone over a weekend at the beginning of the month, and you know them on a social level (i.e speaking informally), I would say "are you free any of the weekends in early November?". As above there are a few different ways of expressing this. Given there are normally 4 weekends in a month you could ask "Are you free any of the weekends in the first half of November?". If you need to ask more formally I would say "Do you have availability to meet up on one of the weekends in early November?".

Are you free...?
This always seems like a rather strange thing to say (for me;-)
Are you available might well be a more suitable choice of words.
Since almost nothing "is free" in reality,
So I prefer to be as concise as I can when using English Phrases...to avoid confusion.

"Are you free on the weekend during the first half of November?"
This sentences is asking whether someone is 'free'/available (not busy) during the first half of November, this is implying the first 2 weekends of November.
"are you about on the weekend during the first half of number?"
'Are you about' is a casual expression used to ask if someone is free or available.