March is not a low season for traveling but also not a high season. From Guangzhou to Beijing, you can travel by train or plane. It is hard to say which one is cheaper now. Normally, taking train is cheaper, but sometimes, the flight tickets have good discount and the fare would be lower than train fare. So you can wait till next year and make dicision according to the real condition. Guangzhouhas only one airport and the train station is about 50 kilometers from the airport.