1)
Where did Yad Hashem come on him?
1.
Radak: In Tel Aviv.
2)
Why did Hashem tell him to go to the valley?
1.
Radak: It is more Tahor than Tel Aviv, where people dwell. Hashem taught to him time after time to make him understand Hashgachah and [Hashem's] conduct. Also, in that valley where Bavel was built, He showed to him Hashgachah in the creations. There Hashem confused people's languages and nullified their intent.
2.
Malbim: (a) It is so he will be isolated, and prepared for Nevu'ah. (b) The nation were not worthy that Ru'ach Hashem come on the Navi when he was among them.