You can go to in Bulgaria over aeroport "Sofia".
Many airlines fly to this airport, including some Low Cost Airlines
You can get information from your local dealer or by visiting this website: (SOFIA AIRPORT)

You can get to Bulgaria
by train get information from your local dealer or look here
by bus get information from your local dealer or look here

Taxi option in Sofia.

You may book a taxi from the office situated at Arrivals hall (Terminal 2)

The official taxi company that operates to the airport can be found here

You may book a taxi OnLine at OK Supertrans site. You can do this up to 3 days in advance of your arrival via the online form OK Supertrans booking.
In addition you should request to receive a preliminary estimation of the price.

NOTEs: Your arrival point is Terminal 2 on the Airport.
We suggest to use only certified taxi companies. All licensed taxis are yellow and have a price list of a car windscreen (look at image above)
Route taxi (Terminal 1 - Terminal 2): Work time: 7:00÷19:00; Interval: 30min

Public transport in Sofia. fare for a single journey 1.60BGN

More about urban transport lines
Urban Mobility Centre (click)

Public transport that you could use

The metro of Sofia. fare for a single journey 1.60BGN

It is really new, it started operating in 1998, but it has quickly become the favorite means of transportation for citizens. There are two lines, which are connected at the Serdica station. The metro also reaches Terminal 2 of Sofia Airport. There is a also a new line under construction.