A bird in the hand is worth ten in the bush.
Although there is something to be said for going through formal recruitment in the fall, if you go through informal and find a group you like... Take the opportunity and don't wait.
I would never encourage someone to choose a group just to choose a group. But there is no guarantee you will find a group to join if you wait until the fall. You might be ill, you might have a family emergency, you might hate the formal recruitment process, etc.
I went through informal and sometimes I wonder if I would have ended up somewhere different if I had done formal rush. But I think I would have hated the hugeness of it and probably not made it through all of formal. I'm glad I took advantage of the opportunity I had.
Again, don't join just to join. But if you are really interested in being in a sorority and find a good fit now, go for it.