Demographic Composition: Bulgarians 87.9% Romani 1.5% Turks 0.8%
Average Female Height: 164.8 cm (5 ft 5 in)
Vitosha Boulevard is by far the busiest fully pedestrian street in Sofia, therefore it gives you the best chances to find solo girls, you can start walking from Serdica metro station (an important transport hub) and head towards the National Palace of Culture. There will be a good number of shops, coffee shops and restaurants on your way, at the end there is a large park often used by locals for leisure walking.
If it gets dull you can go to Not far from Vitosha you can find the less fancy Graf Ignatiev Street, several of the landmarks of Sofia are located along it, many tram lines feed the street with foot traffic.
During university season its worthy to go to Tsar Osvoboditel Boulevard through the City Garden, you will reach the University's metro station, a good source of young female students to approach, bare in mind that it would take you a while to go there from Vitosha.
Unfortunately, Sofia city centre does not have a big mall to retreat to in case of bad weather, TZUM shopping centre is in the area but it is only good to go to the toilet as it has very little foot traffic. In case of a rainy or cold day your best bet is to go to the largest mall in Bulgaria: Paradise Center, a 330+ stores shopping centre you can reach by metro.
Best times to visit
Sofia enjoys nice weather from april to october, however, during the peak of the summer (july and august) the city becomes too hot for people to walk around in significant volume during most of the day.
Also, small cities like Sofia suffer from a lack of serious young female volume during the university summer break (july to september) which leaves us with May, June and October as the best months.
Bulgaria has a Moderate proficiency English First English Proficiency Index score of 59.37, most girls you will find in Sofia will be able to speak to you in English.
See wikipedia article.
Bulgaria is a member of the European Union but it does not make part of the Schengen area. this means the following:
If you are a EU citizen, you can stay as long as you want (blue and yellow in the graph)
If you are in the green countries, you can stay in Bulgaria for 90 out of every 180 days even if you run out of your Schengen Area days.
Gray countries need to apply for a visa
Numbeo Apartment (1 bedroom) in City Centre Average Monthly Rent: 402.07 USD
Bulgaria's Average Airbnb price per night: 35£ (49 USD) according to Vouchercloud
Numbeo cost of living data:
Arriving to Sofia
Check out the 'Get In' section in Wikitravel to know how to get from the airport to the city centre.
I believe the best method of street game is the London Daygame Model. I recommend the key textbook Daygame Mastery. It's an encyclopedia of street game technique. For video, I suggest the infield instructional Daygame Overkill.