He was ignorant to the fact that a Navy Admiral was on the island as their enemy.
He endangered the crew by creating a risk for that same Admiral to be alerted to them, as well as Doflamingo and his army. Did he have a valid reason for running? Yes. But there was an even more valid reason for him NOT to run off like he did.
Yes, people were looking at them. You can see Zoro's dash out the restaurant making noise that caused people to look over at him here[
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] and he was yelling for his sword and at Sanji in the middle of a crowded plaza.