Original A: I don't know whether to turn left or right. (= I don't know if I turn left or right ?)
The first version is fine. There needs to be a "should" in the parenthesis version.
I don't know if I should turn left or right.
Yes, they mean the same thing. Note that there are only two options here, you either go left or right (in B you have three options).
Original B: I don't know whether to turn left will take us to the hotel. (= I don't know if turning left will take us to the hotel )
Note that if you just write left (instead or "left OR right") then you are saying "... should I turn left, right, or keep going straight... (unless there is no straight path and the road splits in opposite directions).
The following is how I would say it (BillJ in his comment says the same thing).
I don't know whether to turn left to get to the hotel. OR, I don't know whether turning left will get us to the hotel.