Closed meetings are for members or prospective members. Most Alanon meetings are closed. This is what I have just read on their website. I assume open meetings mean anyone can attend and not necessarily someone who has had problems with alcohol perhaps someone else can clarify.
You are a prospective member, so definitely included.
Hopefully you will find Al-anon of some benefit to you. Go to a few meetings and a few different places too if you can. Sometimes one clicks more than another with different people etc. I try to get to two meetings and one is definitely my favourite just because of the people who attend regulary and the wisdom shared. You have to be a bit open too as meetings can take some getting used to.