You may want to read the answers to the question When during the application process should a candidate mention that their spouse is also looking for a job . In general, there are several positions on when to acknowledge a spouse, and none of them is clearly "the best" for everyone. The gender of the applicant, the type of school, and the particular two-body problem are all factors.
You actually have the "better" kind of two-body problem, because your spouse is not looking for a job at the school. You would want to make that clear if you mention your spouse. There are two main concerns about the two-body problem: (1) the school may not have a second position already secured, and so letting them know you need two positions makes them less likely to offer you one; and (2) the general potential bias that claims "someone who is married will be less dedicated to the institution" (this is why some people don't wear their wedding ring to interviews). In your case, the main issue is how you feel about (2).
But didn't you already indicate in your cover letter some reasons why you would be willing to relocate to their location? This is one of the things that a cover letter should always include: some reason why you not only want to be at their school, but also want to live in that area. For very prestigious schools this is less important, but for smaller schools they may take the question very seriously. If you didn't include anything like this in the cover letter, be sure that you have something to mention during the interview.