I didn't get the benefit of a choice (to propose right before b-school) since I proposed to my fiancee before I started the application process; but I am very happy with my choice. She was very supportive and traveled with me to schools when she could. This was great because she noticed some things about schools that I didn't pick up. She also provided some good feedback for my essays, but occasionally I had to reject some of her ideas.
We're both excited to move to NYC after we marry next month. She understands it's going to be tough since I'm the breadwinner; yet, she's been very supportive about this too. I think the most important thing is that we really want to spend the rest of our lives together and start a family after b-school, so it doesn't matter where we are, if we're broke for 2 years, or if I'm going to be extremely busy (especially if I choose to do IB).
If I had to choose to propose to her now with the knowledge that I'm going to b-school, I would still do it. This is the most important question you have to ask yourself: would the two of you want to be together regardless of the circumstances?