Just came back from the trip and thought I would follow up, for future reference if nothing else. Thanks for all the tips guys, definitely helped us out.
So, Sofia was an absolutely awesome place. Wild as fuck, especially compared to Sweden where we're from - random shops in every nook and cranny, cats and dogs wandering the streets, people hauling shit by horse and carriage and huge pine trees rising amongst the concrete buildings.
All locals we spoke to were super helpful, skaters and non-skaters alike. We randomly ended up in a bar, seeking shelter from a rainfall, and befriended a bunch of great people who guided us through a wild night of rooftop concerts in an old art gallery, night clubs being run under the radar in the basement of a soup kitchen and where to find the best night snacks to remedy all the previously mentioned frolicking.
The food is insane - so good and for no money at all. Get a hearty bowl of the best soup you've ever had with some freshly baked bread and cup of coffee for 3 leva (€1.50-ish). A good beer for half that.
Sofia is a hella old city with lots of history to learn about of you're into that and the whole city is surrounded by mountains thousands of metres high. Make sure to take the super-long and sketchy lift to the highest peak called Cherni Vrah - the view up there is insane and worth the hour-long hike. Check out the old churches and cathedrals - they're pretty intense to experience especially if you aren't used to the grandeur of old orthodox Christian buildings.
Skating-wise, the city centre has a lot of cobblestone streets, so it's not just pure cruising bliss, but marble plazas like NDK (@all.day.ndk) more than make up for it. There's also a semi-sketchy DIY park in the South Park that is photogenic as fuck. Bring a broom to clean the broken glass, gravel and bloody needles away though. In this area you also have some of the most perfect hill bombs ever - freshly paved roads, no crossing streets and little amount of traffic.
There's a couple for skateshops in town, but the legit one is called Blok and is just by the NDK-plaza. Grindhouse Bar is well worth a visit - indoor and outdoor miniramp, cheap beer and seriously fucking good burgers. A lot of skaters hanging out here as well.
Check out Doom Bar for a drink, Daro Cafe for a hangover curing breakfast, and every corner stores small porch for a nice place for beer, cigs, and shit talking.
Oh, and take the time to memorize the Cyrillic alphabet, it'll help you loads.