Hi Chris,
If you can't get to birdtours, let me know and I'll e-mail a copy. Opened fine for me just now though.
Sorry, no idea about car hire in BG - I used public transport. Didn't need to know the language either, as the Bulgarian lad I went round with has very good english.
On your own, knowing a little Bulgarian or Russian would certainly help a lot, and even more important, to be able to read cyrillic road signs (major road signs have roman script as well as cyrillic, but smaller places and back roads don't).
Getting around - the roads vary from mediocre to dreadful, and there's still a fair deal of horse- and donkey-cart traffic, so expect journeys to take 3 times as long as you'd expect from the milage involved. At least the cars (Moskvitch, Trabbies, Skoda) tend to be built like tanks, so they can cope with the potholes well.
No problems on entering the country, maybe because of the long queue at the entry - it was the day before the Bulgaria-Denmark world cup qualifier footie match, so there were about 10 planeloads of Danes on top of the normal airport traffic. Everyone was being waved through fairly quickly, no baggage checks at all, only passports.
On exit, they checked a bit more carefully (just 2 weeks after the Al Qaeda WTC massacre), but still no problems, once they were sure it was a telescope, not a gun or bomb.
Michael