grades

I'm not looking to be in a top house, but rather an upper middle house. I have a 2.9 gpa and am involved on campus. Do you think that having a 2.9 will put me at a big disadvantage?

I see you say "upper middle". Since I'm not sure what you are looking for, I'll give you all mid tiers.
ChiO - will not take a 2.9
DDD - probably won't take a 2.9
KD - your best chance
AGD - Probably won't take a 2.9

Spring Rankings
1 Kappa Alpha Theta
2 Chi Omega
3 Alpha Gamma Delta
4 Kappa Kappa Gamma
5 Alpha Epsilon Phi
6 Delta Delta Delta
7 Alpha Phi
8 Alpha Xi Delta
9 Kappa Delta
10 Pi Beta Phi
11 Alpha Chi Omega
12 Gamma Phi Beta
ALL - Undergrad Women 3.23 3.23
13 Phi Sigma Rho
14 Delta Gamma
15 Delta Zeta
16 Alpha Omicron Pi

Fall 2013 Rankings
1 Kappa Alpha Theta
2 Chi Omega
3 Alpha Gamma Delta
4 Kappa Kappa Gamma
5 Alpha Epsilon Phi
6 Alpha Phi
7 Alpha Chi Omega
8 Kappa Delta
ALL - PHA 3.37 3.34
9 Pi Beta Phi
ALL - Greek Women 3.36 3.33
10 Delta Delta Delta
11 Alpha Xi Delta
12 Delta Gamma
ALL - Greek
13 Alpha Omicron Pi
14 Delta Zeta
15 Alpha Omicron Pi

in response to the legacy and this one, most chapters dont have time to go through any reasons and excuses. If its a number thing they are going to cut you real quick.

I'm not sure there will be enough time to apply the Freshman Forgiveness in time for recruitment. They will use whatever grades you get for Fall.