I echo what everyone else has said.
As a student who has taken my training solely in the USA (Florida), and been working as a flight instructor on a Visa for nearly a year, I've seen good and bad things about my own flight school, and others.
Mimicking some things that other have said as well:
- DO NOT pay large sums up front. I have to echo what everyone else is saying here, it's stupid, and you're putting your money on the line. So many schools close down, don't do that mistake, you might never see them again.
- Get opinions from students/instructors who have studied/worked at the school(s) you are considering. I don't care what their admissions officers say, their only job is to get you enrolled. Previous students/instructors (hopefully) have none such agenda
- If possible, tour the school, talk to current students, try to find any potential problems with the school. Problems such as: poor maintenance, bad ratio on students vs instructors (in the sense that you wont fly enough), not enough airplanes vs students (again, that you don't get to fly enough).
- If your plan is to work as an instructor, ask current and previous student if the school hires all their students. (Most schools do, because they can take a huge advantage over something close to "free labor").
Lastly, look at the kind of training you will have to do. More and more schools REQUIRE you to do silly additional courses that are not required in any sense by the FARs or part 141 training.
Like extra ground schools, extra flight training not affiliated with any type of 141 course, etc.