I don't think that Gandalf had any intention of taking the Pass of Cirith Ungol. When Faramir told him of Frodo going that way, Gandalf was in disbelief. He had no idea why Frodo went that way. So obviously he had no intention of going that way. But I still don't see any other plans he had. As it was mentioned before, Sauron would have controlled Middle-earth by the time they took a longer route. So, I guess that the story wouldn't have worked if Gandalf hadn't fallen in Moria. How ironic.
