I think you can get a cab from airport direct to Bandung, it'll cost you around Rp 450,000. That's what I did last time. If you notice, people on the net always suggest to take the blue cab, make sure you take one if you choose to go there by cab. Train is bad option, yes even though te distance is less than 30KM from airport, but it's gonna take almost 2 hours! Good luck