Don't quite agree with the post. Visa waiver only allows you to do business or tourist. If you enroll in a training program you will need a student visa. Wether you finish (get the check ride) is rather secondary as you are training and enrolled in a program. That would also go if you go with a friend who is an instructor and train - in which case he has to make sure you have the proper documentation.
In short: VISA - YES
TSA Clearance - YES