Here are my tips, for any readers that are seriously trying to get into the business...
1) Get good work experience. There is enough demand for these kinds of jobs that you're not likely to get hired right out of school. So get good experience in an area you like - there are a whole lot of disciplines used in theme park design. Engineering, architecture, set design, costuming, project management, the list goes on and on.
2) Get volunteer experience related to themed entertainment. There are plenty of opportunities, and this adds to your resume and shows your commitment. Get involved with local haunted houses, zoos, or museums.
3) Learn as much as you can about the industry. Visit the theme parks, go to the trade shows, and try to learn as much as you can about what goes on behind the scenes. Know what's new and the companies involved, and you'll sound like you know your stuff when you finally get an interview. (I'll never forget the Imagineer who began our conversation by saying, "So, you've been to all our parks?")
4) Move to where the jobs are. I'm afraid that if you're in Kansas applying for a job in California or Florida, you're probably going to be out of luck. Relocating to where the jobs are shows employers that you're not just a person who wishes they could design theme parks - you really want to get into the industry, and are willing to take some risks pursuing your goal.
5) Network. Tell everyone what you want to do, even if they think it sounds silly. If you're in one of the main theme park areas (L.A. or Orlando), it won't take long to start connecting with people in the industry. There are lots of them!
6) Be patient. A lot does, unfortunately, come down to luck and being in the right place at the right time. No matter how amazing your skills are, a company isn't going to create a position for you unless they have a need to fill.
So good luck to anyone out there who is trying to get into theme park design. It's not easy, but if you really want it, you can do it. You just have to be the person who wants it so much, that you won't give up when roadblock after roadblock gets in your way.