You need, like me or anyone, to read this wonderful psalm really through, all of it (really!), and then we better have the sense of it. And it helps to have read other psalms and know that David often used hyperboles in his psalms (the hyperboles are of course helping point us to the truth but are still hyperboles, and thus that broader reading is entirely needed). When you read through the entire psalm, then you will see the last 2 verses, and they help us get the entire psalm.
Psalm 139 NIV
For those still not convinced there is hyperbole and poetic wording (which speak to the essential truth), consider:
Psalm 139:15 My frame was not hidden from You when I was made in secret, when I was woven together in the depths of the earth.
Does this mean that babies are actually made underground and then teleported into their mother's wombs? Of course not. It's poetic. It's also true in essence. You just have to listen to the entire psalm and not quit before those last 2 central, key, verses.
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Ok? So, the answer is in my best guess 'yes -- generally God knows what we are going to say even before we say it'. This isn't the same as a totally deterministic life though! You also kinda know that it's going to rain just before it does, if you look up at the sky and notice the cool moist breeze that just hit you before the rain.
How much better can He see us and know us than even we know ourselves!
That still doesn't at all mean He designed us to be totally predictable in every last moment though.
This is all a very deep mystery, as it involves things (in my view) such as 'what is consciousness' and 'what is spirit' -- it is as deep as mysteries ever get so far as I know so far.