It took me about 6 weeks to lose the first 20 pounds. I don't think I'm typical though - just lucky that my body responded really well to the changes I was making (I was also nursing, which can help some people - and I think it did and does help me with my loss).
I'm close to your start weight. Last March, it took me 2 months to lose 20 pounds. Now since I started again in January, I'm down 26 pounds in 9 weeks.