Time traveling is one of those speculative issues. I will take your question and add that you would only be an observer who could not be seen by others. Thus, you could not change what has happened if you go into the past.
Now, I would choose the past over the future, because we do not have a road map to the future, so how far do we go into the future? What would be a good year or century. Would knowing the future allow us to alter it and would not be good or bad, because we could not predict the unintended consequences of our actions.
Thus, I would like to into the past and since I studied a lot of American History, I would to have been at the Continental Congress when it was working on the Declaration of Independence. To hear how people with such diverse interests came up with such an outstanding document would be an amazing experience.