To answer your questions:
1) May 17, 2004 is the start of the 2005 AADSAS application cycle.
2) The DATs should be taken ~June-July. August would be a little late, but not impossible. Don't try to push it onto September.
If you say you don't know anything about being pre-dent, I'd advise you to hold off on your application until the 2006 cycle. If you don't have any dental experience now, it'd be a little disadvantageous to you to apply now. Plus, how do you know you're going to enjoy doing it for 20, 30, 40 years if you don't have at least a little exposure?
I think Eric is trying to be a little too optimistic, sorry. It's not a 2.0 or below. I know there's a 3.0 and under club here, but get the highest GPA you can. You don't want to be playing the odds when you have a 2.7-2.8 GPA with only mediocre DAT scores. To be successful, I'd say 3.4+ GPA, 20+ DATs for a very good chance of interviewing at most schools you apply to, private and in-state.
Next, if your school doesn't have a Pre-Dentistry club, don't worry. I never did much in my club. Like most everyone on SDN, I took the initiative to go out there myself and learn about Dentistry myself. If you're interested, learning about it should be fun, not a chore.
If you have any more questions, feel free to PM or just post again and I'm sure someone will be happy to answer your questions.