Very conveniently, Kraków has its own international airport (John Paul II, or KRK), with most major airports of the world a single connection away, and there are numerous direct cheap and regular flights to many European cities. The direct flights can be checked at the KRK website. The airport is connected with a direct train line to the city center (a ride of 17 minutes); a taxi ride would cost you ca. € 20.
Train journey to Krakow is also a possibility, especially if you want to combine your stay there with a longer stay in the area. That would be a good idea if you wanted to explore Kraków together with the other jewels of Central-Eastern Europe: Prague, Budapest, Vienna. Also, express trains take you north to Poland’s capital, Warsaw, in 2.5 hours. This and other options can be consulted at the Polish Railways site.
If travelling in family/friends mode, you might want to consider renting a car anywhere in the general area. Berlin is not a very long day’s drive away; Vienna and Prague even less than that. Driving directions to the conference venue from your location are perhaps easiest to find here.
Once you get there, Kraków is a very walkable city and it also boasts of a reliable public transportation system. Most of the conference hotels (including budget accomodation) are within 15-minute walking distance (probably less); a 20-minute bus or tram ticket is ca. € 0.75.