Before he even made any attempt at conquering Yerushalayim, Sancheriv first "went up against all of the fortified cities of Judah, and conquered them" (II Kings 18:13). This was eight years after the last exile of the Ten Tribes (as shown by comparison with v. 10 there; Seder Olam Rabbah 23 points out that each successive exile was eight years after the previous one).
So yes, evidently he deported the Jews living in these cities. (Lehavdil, Sancheriv's own account has him conquering 46 Judean cities and exiling 200,150 of their inhabitants.)
Seder Olam there goes on to explain that (as Nachum pointed out) Sancheriv then decided to bypass Yerushalayim and go off to conquer other surrounding nations: Ammon, Moav and Ashdod. Even later, after he had already started his siege of Yerushalayim, he broke it off for a while to go and conquer Egypt and Cush, then returned to finish where he had left off. The result was that when his army was miraculously destroyed, all of the wealth of those nations fell into Jewish hands.
So what actually happened to these Judeans? It doesn't say. Could be that indeed they were sent to the same places where the Ten Tribes had been sent (and didn't return afterwards), or perhaps Sancheriv had them marching along with his army and they were therefore present that Pesach night when the Assyrians were killed, and were able to return home.