You don't have to say anything if you don't want to. I'd suggest arriving 10 mins before the meeting start time so you'll be walking in with others arriving at the same time.
Likekihood is that someone will come over and shake your hand and introduce themselves. We're a friendly bunch. And you know, NONE of us forgot our first meeting and what its like having to walk in that door the first time. We all remember , and we empathise with every newcomer that arrives.
Open meeting means it's open to alcoholics and those with an interest in helping them. Closed meetings are for alcoholics only. You would be able to attend either.
Good luck, not that you'll need it. Let us know how it goes.
Hugs to you.
BB