inappropriate language

Hello, just found this site and hope to learn alot.  Here is my situation:   I am in a relationship with a 45 year old male with ADHD.  He takes meds (concerta) and I have only known him since he has been taking it (so I don't have any sense of whether the medications help him or not because this is the only way I have known him). Here is my problem:  He has a horrible potty mouth! He uses the "f" word at least twice in every sentence.  I've explained that it offends me. I've explained that it makes him seem hostile, inappropriate and/or uneducated.  It just rolls off his tongue endlessly.  I notice he doesn't speak this way in front of his family though (which means he CAN PRACTICE SOME SELF CONTROL AND PERSONAL CHOICE in the words he speaks, right?) I am frustrated beyond belief.  I have, on occasion, sent him home due to his foul mouth. It's difficult enough to have a conversation with an ADHD'er without trying to filter through all the foul language.  I am curious, has anyone else experienced this? Is this just his personality and has nothing to do with ADHD? I'm stumped, help! Any input/advice welcome.