If you sign up for a (free for 30 days) account on IBM BlueMix, it is simple to use a pre-canned IBM Watson instance that contains medical information and travel information. Code samples are provided for Java, node.js, and Ruby. I wanted to use Ruby so I used these setup instructions.
IBM BlueMix uses the Cloud Foundry PaaS tools. If you have any experience using Cloud Foundry then setting up a (free for 30 days) BlueMix account, and deploying one of the sample web applications that uses the pre-canned IBM Watson medical and travel instance can be done in about 20 or 30 minutes. This is a worthwhile exercise because once you deploy your sample web app you can experiment with IBM Watson's ability to parse natural language questions and return relevant data. Very nice stuff!
In order to build a custom application using IBM Watson you need to supply training documents and training questions. I am helping a customer do this right now. Currently you need a partnership arrangement with IBM to train your own IBM Watson instance but I believe that the ability for anyone to do this via BlueMix will be available in the near future.