If it were me, I'd just say all that (you're planning to bid, but will be in the area for a couple of days; you're very interested in the firm, and would be available to meet then, etc).
My guess (and completely a guess), is that it's better to just try and ask - they may have a policy for everyone to funnel people into OCI whenever possible. If I were recruiting, though, I'd at least ask for a resume from someone in this position - if it was someone I'd be interested, I'd actually rather interview them early, and then open up another slot to see yet another candidate from the school during OCI. It just makes sense to me to try to interview as many qualified candidates as possible. But that's just my thinking, and I'm clearly not in position of a firm recruiter.
So I say just ask politely; the worst that happens is they say no, but perhaps make note of your name as being very interested in the firm.