Hi,
I can assure you that most of the Bulgarian dentists are really good specialists. And they work in quite low prices (especially compared with the American standards), so don`t postpone it and just go somewhere! Most of them, especially the younger dentists, know English quite well, so you won`t have problem with this. 
When I chose a dentist for myself, I`m checking those stuffs: to be a man (because I think they`re better specialists), to be young (not more than 45-50 years old, because of two reasons - first, younger specialists try harder to improve themselves every day and second, their profession is very hard  and I think that after more than 25-30 years of practice your hand isn`t  as sure as it was when you were younger) and the dental office has to be nice, clear place where everything that goes in your mouth is sterilized. The last one these days already is a rule for most of Bulgarian dentists, so don`t bother too much!
I wish you luck with the dentist and hope that soon you will share your impressions and experience!
You may also search in this site http://www.bzs-srk.bg (it`s the official website of the Bulgarian dental association, Sofia region)