Peels especially salicylic acid are the best for that ( it also helps with the active acne! I have been doing peels weekly and my marks go bei 1 to 2 months ( 20 % salicylic acid peel ). Search for ROBERT's posts about salicylic has no respect in this board. You will find lot of helpful tips.
What brand of SA are you using? I am using the Neotrata ( Neoceuticals 2 % SA : high amount of alcohol !!!) since 1 month and the results are not very noticeable. Mornings i am using the 10 % AHA + 2 % hydroquinone also from Neostrata and a weekly 50 % Glycolic peel.