No, you cannot assume the reader has watched the program. For example, I watch very little television and would likely not have seen the program you are reviewing. Therefore, you must provide a quick summary or work into your review enough of the program so that a reader can follow what you are saying. Maybe the reader normally watches the program, but missed either all of this edition or maybe part of it. Either way, your review must be comprehensible by anyone who reads it which means that they must understand the program to which you refer especially if they have questions or don't agree with your review.