I would have thought you could undertake the ACE from anywhere that has decent Internet access. It sounds like one of those things where if you have to ask, you ain't ready for it.
You can use the Classroom in a Book and the Photoshop help to prepare. However, the CIAB series is NOT specifically written to help you prepare for the exam but to learn how to use Photoshop, and you will need to sit with the Exam Guide published by Adobe and work out which areas of help you should study (this can be rather hit and miss, and definitely time consuming).
On the other hand, we at Examaids Ltd, have done most of the hard work for you and created standalone, interactive applications for Windows and Mac OS that can help you to prepare for the Adobe Certified Expert (ACE), and the Adobe Certified Associate (ACA) exams.
We have unsolicited testimonials and demos on our website that you can try before you buy.
[post edited by mod, links removed]