I personally don't see anything wrong with meeting someone at a bar, my friend met her husband at a bar. I think the whole stigma attached to meeting someone at a bar has more to do with going home with that person that night, both people drunk.....you know what I mean? In any case, he sounds like a good person and I think you should call. Just be careful, (although I would give that advice no matter where you met him). And, if he's interested in learning more sign language from you, I think that shows that he's interested in more than just taking you home for the night. Just my own opinion.