I really don't have any smart ideas. Beside the usual computer/internet solution and the under mattress/pillow one.

Well... take this seriously or not. You could learn to write in code, I have this cool book which talks all about that. Maby even learn some other forms of writing like several versions of ancient nordic runes or the cyrillic alphabet in different combinations. Design your own. Since you know english, doing that shouldn't be too hard. You might see this as pointless and too much work, but I think I might get into this sometime soon. Sounds like fun to me. I doubt that people would bother with decyphering it. Unless they go really nosy and send it to CIA or something.

If you are feeling artistical then maby you could just draw some sketches and graphs with added short descriptions.

Whatever you do, Good luck!