I work at a flight school out of DVT in North Phoenix. I will tell you one thing, most of the CFI's that I work with that went to ATP regret getting so much into debt because they went to ATP and not just that but they actually hated that place. This coming from about 5 different guys that went to ATP, they all agreed on one thing, ATP's marketing is really good (0 to hero in two years or whatever) that's how they get you.
Do it at your own pace, paying as you go if you can at a different flight school.