I changed so far 165 villages and town to have an int_name/name:en.

At first I downloaded a map from three tiles for bulgaria for garmin
from http://garmin.na1400.info/routable.php .
But my garmin has no cyrillic letters, so I had a lot of '????' names.

Look at @wieland/edits for my changes.

There are still 85 towns and a lot of other names (peaks, etc.).

I know there are different ways to write names in latin letters.
I did: "Я" -> Ya, "Ю" -> Yu, ...