Ok, if we are to believe what Anthony Cooper said, He was driving on I-10 when he was forced off the road, he awoke looking at Locke. This jibes with when Ben told his gofer to get "the man from Tallahasse".

so either
1-they went off the island to get Daddy Locke and returned within 1 night just in time to have John blow up the sub.

2-They already went to Tallahassee to pick up Mr Cooper and had him unconcious for days until just before Locke opened up the door to his room, so the first person that Anthony Cooper would see would be Locke.

or
3- There is a way on and off the island and Ben is lying to the rest of the others.

will the rest of the others catch on to Ben's "untruths"?

I think that when Richard Alpert was comming back after the plane crashed they told him about Locke and try and find him, he finds him and them stages an accident and then brings him to the Island