Since we know Jefferson's car from the end of episode 2 (TPFTHLK), we have his whereabouts from David's notes.
http://i.imgur.com/plTvfCa.jpg
http://i.imgur.com/9675tSn.jpg
Unfortunately, the game
starts on October 7, so all we can see are that Monday and the week leading up to it. Should be fun to map out his path and cross reference it with the locations we know and Nathan's whereabouts. Frank's book doesn't have a codename for Jefferson, maybe locations will match up and he'll have a pseudonym.
We also aren't given the GPS coordinates of the locations themselves, so we'll have to match them up with David's notes. Looks like some major stuff happened 9/30 as well with the amount Nathan was at his family's estate.
edit: Double checked, Nathan gets
Gamma-Hydroxybutyrate (date rape drug) at Blackwell at 10pm.
Makes you realize David knows more than what we have in his notes if he was already following Jefferson.
Code:
Prescott Estate: 45.531822 -123.921232
Barn: 45.496698 -123.894625
Junk Yard: 45.552381 -123.925695
Beach: 45.547693 -123.935308
Blackwell: 45.535068 -123.906641
Gas Station: 45.528334 -123.931704
Forest: 45.557069 -123.90132
Diner: 45.542283 -123.929815