Here’s a good article if you’re spending your Saturday night on the Internet: Bipolar Disorder and Dating. Bipolar World offers some cautions and concerns for both the bipolar and non-bipolar partners, including this:

Another consideration for those with bipolar disorder and dating is when one should tell the potential partner that they have bipolar disorder. This is a very difficult decision. In my experience it is not something that you want to divulge at the very beginning. If you do then you can expect the non-bipolar partner to immediately withdraw and probably terminate the relationship. This is due to their own judgments and rationalizations about what bipolar disorder is and what your behavior will be like. This is usually unfair. It is much better if they learn to judge your behavior based on its merits rather than simply assuming that because you have bipolar disorder you will do certain things. We are all in different stages of the disorder and some have learned to manage their symptoms very well. Yet by telling someone that they have bipolar disorder at the onset of a relationship they could very well find themselves judged unfairly.