The Veiled Alliance was not founded until close to FY -500, so no. But a similar organization left over resistance from the Cleansing War may still be around.
Celik was destroyed in the Green Age per the Timeline of Athas.
Depending on how close to Dregoth's death you start, the dragon is still rampaging for 25 years after Dregoth's death. If you are in that time period, the other kings are probably keeping their cities locked down. I would image there would be little to no travel or trade between the cities. Any merchant houses that exist would be limited to one city.