A few thoughts on the listen or talk topic.  If you plan to demonstrate
the piano to people who are not familiar, give a brief introduction
about how it works first so there is less of an excuse for interruption
with questions.

If people do interrupt with questions, either politely suggest waiting
for the music to stop or stop the music and then start it again after
answering the questions.  Most people will get the hint after a few
sudden stops.  Those who don't can be asked to talk elsewhere.

Be sure to pick appropriate music if playing to people who have not
heard these machines.  Each system has at least a few killer rolls that
anyone would enjoy.  Make it lively and short to start.

Consider that it might be that the piano isn't really that great.  You
may be used to hearing it and compensating for the deficiencies but for
someone not used to the piano, it might be too much to endure.  The
same is true for a very loud piano.  Personally I like concert level
performances but understand that a lot of people never listen this way.
Music is part of the background and rarely the focus.

I find that friends who are seriously interested in music (no matter
what kind) are less likely to talk during a performance.  My best
listener was a Grateful Dead fan.  The first time I put the piano on
for him, he went to the most comfortable chair in the room, closed his
eyes and got a big grin on his face while he enjoyed the piano.  We
talked a little about the piano when the music stopped and he was ready
for more.  Unfortunately this experience is not that common.

Best regards, 
Spencer Chase
Garberville, California
http://www.spencerserolls.com/