Yes, any who attend are viewed as ones who are interested. This is one spark of hope that is given to the JWs every year to give the appearance of the future growth to come-- WHY look at how many more attended the memorial--they are all potential victims (AKA bible studies).
So it goes that every faithful witness is encouraged to drag along anyone they can for the big night of passing the bread and wine around. I think that the majority of non-JWs who attend are not interested at all, but do so because they are relatives of JWs and figure it is their one big event of the year so what the heck (they may also feel somewhat sorry for the JW relative as they seem so pathetic over this memorial thing). Others are forced to go in one way or another--they are put into a position where they just can't say NO when a rabid witness just won't take any clue that you don't want to attend and offer you everything if you go--will save you a seat--pick you up at 7:00--hold your hand--take you out for icecream afterwards--anything to get you to attend. We were all given complete instructions on how to get others to attend --the Org created this mania every year around memorial time...