If I wanted to hear the speaker, I would go. I don't consider anything other than their office and their home as belonging to a therapist. As long as one is not going just to run into the therapist, I don't see a problem with it. Or if it will wig you out (not the therapist but the client)- then I would not do it.
The first therapist I saw used to go to concerts (women's music, comediennes - small venue specialized topics) that I attended. To keep with the language -it was my turf (lesbian) and not hers (straight). It was not a problem although we did see each other. I stayed away from her.
The therapist I see now, I don't think would recognize me or me her out of context.