I went to ATP Long Beach in 2005 for the same program. I ran into weather and maintenance delays, but I got lucky and was able to finish on schedule, even though I only had 5 days. In retrospect, I should've gone to Vegas where the weather was less likely to be an issue and the fleet was bigger.
As others have said, show up ready to perform on day one. My experience was with a 300 hr given CFI who knew the gouge on the examiner and the airplane and had the FARs memorized, but couldn't really teach otherwise. (He told me one of the reasons a twin had a left-turning tendency was because the accelerated slip stream was deflected to the right. Huh? He also handed me a lesson on ILS and said, "Copy this over in your own handwriting." I elected to write my own lesson, the examiner asked me for it but didn't even look at it. Instead, most of the two orals was spent listening to him tell me stories of flying in the Battle of Midway, winning the Navy Cross, bombing the Yamamoto, and working in Hollywood after the war. Very interesting stuff, but not really typical orals.) My CFI was a graduate of ER, and I don't think he ever took a pleasure flight in his entire life, and it was reflected in how he approached flying. He had what I was after though -- the ability to endorse my logbook to take the tests. That's what I paid for, and that's what I got. Nothing more, nothing less.
When I enrolled in the program I was a CFI with about 1000 hrs TT and 400 dual given. I didn't have access to a twin at home and it had been over a year since I'd flown one, but I had about 75 hrs of twin time when I arrived. I did have access to a PCATD, so my instrument skills were sharp. Because of my lack of currency in a twin, and never having flown a Seminole, I opted for the 15 hr program. I'm glad I did because I didn't realize until I arrived that my block of time was to include transit from Long Beach to Van Nuys for the MEI, back to Long Beach then back to Van Nuys the following morning. It was 45 minutes each way, and although I did use the time for some training, it wasn't the most efficient hours of flight training I could've designed.
I was happy with my experience at ATP. I live in Japan, so it provided me an opportunity to divert from a business trip to Hawaii, grab a couple of tickets, and be on my way. I don't feel like I learned much at ATP, but that wasn't what I was after. The majority of my learning took place as I prepared myself prior to arriving.
I think your challenge will be to arrive prepared if you attempt to do it over spring break. Knowing that the weeks leading up to spring break will be filled with demands of school, studying for exams, etc. you may have trouble devoting the time required to prepare yourself. You'll probably also be mentally drained after finals week (at least I always was) and the last thing you'll want to do is hit the books again for a week. (That's why everyone goes to the beach instead!) Realize that you'll have to make your decision and stick with it. If you get to finals week and find out you haven't had enough time to prepare yourself, it will be too late.
Good luck and let us know how it turns out.