It's currently $286 on coinmarketcap. I need to buy some ETH to participate in an ICO soon. Is now a good time to buy or do you think it will go down more in the next few days?
It will or it will not. You can buy now, when it still on a lower rate. You will never know what will happen. So if you want to save something, buy now. But if you want to save something more, then wait for a few days. But this is risky, tomorrow, it might be back on rising so you may regret it. There's no hard in risking, if you can accept the consequences and not to much.