The Torah laws of Yichud generally prohibit a man and woman; besides one's wife or mother, (or perhaps even a man and two women) from secluding themselves together in a place that is for all purposes considered "behind closed doors where no one can see or have access". The laws of Yichud are detailed and this answer does not serve to go into them in any depth, as that is not the OP's question. (You should consult your Rabbi if you have a specific situation.)
A general rule is however, that a "publicly open space" should in general be the exact opposite setting of "alone behind closed doors". Then it shouldn't be a problem of Yichud law.
However, if you define "open public space" as a deserted strip of public highway at 2AM, then Yichud may have an issue with that despite the road's public and open nature.
Let's just say that if you are learning Torah with a woman at the Barnes and Nobles coffee table during business hours, you are probably not going to violate Yichud. :)
However, if the woman is married to another man , then such an arrangement would be seriously frowned upon if not forbidden depending on the circumstance, regardless of Yichud.
If she is a single Jewish lady, then there really is no problem. The only thing is that while I am sure the woman will be studying the Torah in all sincerity, the man may just be studying the woman. :) (OK, she might be distracted too if the guy is really nice.)
This would just make the study session filled with distraction. So a man should definitely have enough "non-girl" learning hours so he can concentrate and retain the Torah lessons he so very much wants to learn.
However, it may be that the man in question is quite used to dealing with female co-workers and clients etc. all day. In addition, he may want to get to know this woman who has so much in common (same spiritual journey) to see if they have the basis for a Kosher romantic relationship which could lead to marriage?
Although politics and religion are usually bad topics to bring up on a date, maybe in this case it will help two people to discover each other? If so..Mazal Tov. :)