Well, I always thought so, but others didn't. In any case, it's different to have an actual document with American style dates written by one of the 9/11 hijackers just a couple of weeks before the hijacking. It's no longer a matter for speculation -- there's now hard evidence that Alshehhi used American-style dates. And this was in a hotel registration card, obviously written quickly, without much thought.
with many of them having worked at convenience stores or as taxicab drivers - those are the type of employers that have their employees writing down dates constantly.
Did any of the hijackers actually work at convenience stores or as taxicab drivers? I know that many Middle Easterners and other foreigners work at such jobs, but did these specific people?
Here's an alternative hypothesis for you - the way the FBI has investigated the anthrax attack it has become clear that someone in a key investigative position is an AlQeada agent. That person has done everything they could to divert the investigation from the Florida connection.
This seems doubtful, and there's no real evidence for it. I don't think any one person at the FBI could do that, since people like Rumsfeld wouldn't put up with it.