How to get to České Budějovice
If you would like to fly to the Summer School, you may fly either to Prague or to Vienna (or to Brno where is also a small airport). All the transport possibilities from there to České Budějovice may be found at this website where you may also buy the train ticket in advance (local bus tickets are typically sold directly in the bus).
If you are flying to Prague, you may use the direct bus line from the airport to the main train station. It is called AE express and the one-way tickets costs 60 CZK (i.e. bit more then 2 EUR). You can find information about it here.