I would vote nay. I don't know why but I have a sneaking suspicion when schools say it's okay to bring someone along to the interview that they don't really mean it. But then again, I'm suspicious about pretty much everything. At one interview, a guy brought not only his wife, but his two month old kid. I suppose he wanted to take the wife but she had to nurse. But it made things a bit awkward between him and the rest of the interviewees. However what's amazing is that I didn't hear a peep from the kid all day, and it was a long day. Maybe they crushed some Benadryl and slipped it into the formula.
If you want to bring your spouse or SO along, then bring that person along to see the area. Once you're in a position to choose amongst schools that have accepted you, then bring your SO to second look to see the school if the both of you feel it's necessary. But I don't see how anyone's SO has to see anything besides the city the school is in. It's not as if he/she is going to be going to classes with you.