Man, I don't know why I keep answering these posts like I know what I'm talking about...
Anyway, from what I've heard around the office, the berakdown is like this: If you're willing to go anywhere ATP has an office to instruct, you can be in the office for anywhere from 4 days to a month (ballpark). If you hold out for a location, you may be there as long as six months, maybe more depending on how many people ahead of you want to go to the same office, or how long it is before someone vacates an office opening up a slot.
Time to regionals? Well, my best guess (for what it's worth) is this: you come out of the program with about 280 hrs. TT. You work for ATP and average about 60 hours a month (again, best guess here...). That works out to about 20 months before you qualify for an ATP rating. Add the month or so in the office, and several months looking for a Pt.121 job, and the grand total is about 2 1/2 years.
I've heard of guys going to regionals in less time, some in more. Thats about as ballpark as it gets.