@bythewell - I agree it is a good idea to make sure you take a well rounded course, although you will also want to eventually focus on a single kind of creative writing.
Otherwise it can be difficult to develop the skills you will need to succeed.
However, I think the most important thing when choosing a creative writing school is making sure it is well respected.
Try to take a course where they ask for writing samples in your application, but don't take that as a given that it is difficult to get into. See what they post as their acceptance rates. They might not even look at the samples, after all.
Ask around to see what the reputation of the school is with other writers. You can look on forums and blogs for example.
Sometimes these so called schools are just an excuse to take your money and won't give you any real value at all.