Don't think you'll have much luck finding people who've been to a country that doesn't allow tourists! Betcha Thorntree will be able to answer your questions, though.
Seriously, I'm jealous as hell. You'd best try and see as much as you can, this is such a unique experience. Maybe you can update the Hitchwiki page.
If the Saudis are anything like the Omanis, you'll have a great time.