fall/spring rush

You might as well do recruitment. If you don't like what are you are seeing with the chapters participating, you can just wait until spring (as long as you don't accept a bid). Fall recruitment is a LOT more laid back, and you won't have the disadvantage of competing against the freshman PNM's.

Does anyone know which sororities drop second years the most and why? I'm really leaning toward the Spring, but I don't want to get dropped by the one I find most appealing just because I'm a second year.

This is pretty much everything I've heard about second years rushing:
1) Some sororities are not allowed to give bids to non-first years (this is probably because nationals wants to milk out as much money as possible from each member, as terrible as that sounds), so the girls might love you, but can't ask you back because of their national's rules.
2) You are also at a disadvantage in the sense that if a sorority clicks really well with two girls but they have to drop one, and one is a second year while the other is a first year, they'd drop the second year 9 times out of 10. It's just the way it is.
3) THERE ARE PLENTY OF SORORITIES THAT TAKE SECOND YEARS. If you're a cool, involved girl, I say go for it. You've got a pretty good shot even if you are competing with first years.
4) It definitely helps if you have friends in certain sororities, but one thing to note is that if you end up joining a sorority, you're more than likely going to spend the majority of your time with the girls in your pledge class (i.e. first years) not the second years that you're friends with. So just be prepared for that if you end up joining. Your pledge class is your pledge class, even if they're younger than you.

I am in the same boat. I am a rising second year and really want to rush but I do not want to compete with first years. Does anyone know what sororities usually do participate in informal rush?

Same thoughts as the rest of you, I'm debating whether to rush or not as well. I like the idea of informal rush but do they actually give out that many bids in informal? Or is it only like 1 or 2 per sorority?

what sororitys are doing fall rush? or is it still undecided?

I had this same problem last year, opted to not participate in fall recruitment and wait until spring.
Many chapters take second years, but most will only take one, rarely two, max. Having friends in many of the more exclusive chapters is essential to making it past the first round. Expect heavy cuts regardless. Many second years will drop after first round, but once you make it past round robbins and have the list that asked you back, it becomes less unpredictable -- those sororities obviously liked you enough that they overlooked your being an upperclassmen.

I rushed Formal Recruitment as a second year, and you get invited back to plenty of places, just not the top top tier ones, because when there's so much competition, the sorority would rather take a first year, so they have more time in the sorority and Nationals can make more money (which sounds cruel, but is unfortunately true). I also did Informal Recruitment second year, and I would recommend it. If you don't like the sororities doing it, you've lost nothing and can do Spring rush, but it's a good introduction to the Greek system and you'll at least meet new friends! Plus it gives you some experience so Formal rush isn't quite so stressful.

half of the chapters are doing informal recruitment this year.

I rushed formally as a second year and loved it. You'll find where you're meant to be (as cliche as that sounds), and I ended up getting into my top pick regardless of what year I was. That being said, Piphi, Aphi, Chio, and Tridelt can tend to cut second years quickly. SK takes a bunch of second years for some reason, and DZ, ADPi, Achio, and SDT all take a decent amount (2-4) as well.