I'm in the chapter where I need to find the bandits - mine already done - did I miss a clue in the Naskhel mines??
Have you been to Beregost since then? You sholud meet Elminster there and he points you to right direction. But also you sholud find letters in mines pointing at mage Tranzig in Feldpost Inn. After confronting him your map will update with camp location.
I think you can't find it until you meet him.
Anyway if you want to know it know keep reading. It's nothing spectacular in fact.
It's Northeast from Beregost.