I just did mine several months ago at JAX and would recommend that location. The guy who wrote the program for ATP, Walt Schnamel, teaches the ground there. Walt also wrote the DPE program for the FAA along with many of the regs we now see in the FAR/AIM. That guy is a wealth of knowledge and a pleasure to learn from.
I did all of my flight training at FBO's and other flight schools taking my time, this was my first experience with ATP. Be warned the CFI 2 week program at ATP is a polishing course. You should know pretty much everything before going in there. Study on your own before hand and go through the entry exam with a fine tooth comb. The open book test they send to you in the welcome pkg with the books is a great tool, use it, it works. I studied for about 2 months before my class date. That included doing the prep test they gave as well as some flying from the right seat at my local flight school. I did fine albeit it was stressful and A LOT of work. The other guys in my class who blew off coming prepared and who thought they would learn all of the material while at the class did not fare as well.
This program is what you make of it. It moves very fast and there was NO hand holding. You will be up studying at 7am - 10pm or later at least the first week. Studying and preparing for my initial MEI and then the CFIA and II was across the board much harder than the actual tests but I think that is how it should be. If you bust your ass preparing than the ride should be smooth. That's how it was for me.
This program is a bear, be prepared.