I'm going to two more recruitment weekends and have already been to one, and all the prospectives went by themselves. At least for the visits I've been invited to, they put you up with a current grad student so I would definately not want to impose an extra person on them, unless you have funds to get a hotel room during your stay, then your SO can check out the city while you're going to the planned events. Honestly, for the visit I have already been to though, it was so jam-packed with events that I had little free time so your SO may end up just being bored.