When Will I Start Seeing IPL Results for Acne Scars?

You need an assessment by a Dermatologist to determine if you have red macular scarring which would improve with IPL, or whether you have hyperpigmentation, rolled or box scar, or ice pick scars which would benefit moreso from a resurfacing laser like CO2 or the newer fractionated lasers. 

IPL is not a very effective treatment for true acne scars so I am afraid you will be disappointed.
The gold standard remains ablative CO2 laser resurfacing with Er: Yag a second choice. Due to medical-legal issues, you may have trouble finding a physician to do this. Also, more than one treatment may be required.
Similarly dermabrasion are also effective for this problem as is deep chemical peels.
All three of the above modalities bear a risk of scarring or hyper-or hypo pigmentation.
Fraxel has become popular for treating acne scars and although it is not as effective as traditional laser resurfacing, you may judge it effective enough.
Collagen and Hyaluronic acid fillers for these scars may also be effective.