Welcome and congratulations on a very exciting decision!
I think it is great that you are examining many organizations right now. Find out everything you can about the groups. I realize that every person on this board is taking her own approach to AI, but I strongly encourage you to find one (or maybe two, if you must) organization(s) to focus on after you have investigated several. Remember, if your first choices fall through, you can always begin again. From what I've seen here, approaching several groups at once can be confusing and risky.
It sounds like our experiences are similar. I am 24 years old, and I'm in grad school. I also was friendly with one sorority on campus, but I declined my bid as well. The time just wasn't right then. Now, I'm ready, and I'm excited!
Best wishes for a successful journey!
LM