here.  A few years ago I asked the same question to a message board and got both "smiling is good" and "don't even look at me when I'm nursing" answers.   Some women feel good when people say "hang in there" and others want you to mind your own business and pretend they don't exist.  

I say do whatever you want.   Although I would stop at the "sit next to them and shield them" answer because I don't think we ought to shield ourselves or run and hide when we're feeding our babies.  

A lady at playgroup was complaining that there were only 2 nursing rooms at Disneyworld when they visited recently.   I said "anywhere you can sit down is a nursing room in my opinion".   Of course, anything flat is also a change table in my opinion.   And anything non-plastic can be used as an ashtray.