Although acne isn't caused by not cleansing your face, there's no doubt that regular cleansing is an important step in your acne treatment routine.
Dirt, excess oil, makeup, etc. need to be cleansed away to help reduce pore blockages. Plus, topical acne treatment medications just work better when applied to clean, dry skin.
But over-washing can be just as bad. If you wash too often, you can irritate your skin. (Scrubbing is also a no-no!)
The magic face-washing number is generally agreed to be two. A twice daily cleansing - morning and night - is just enough to clean away all the extra stuff hanging around on the skin, but not enough to be irritating.
If you get sweaty or especially dirty, a third cleansing might be needed. After gym class, maybe?
Remember, cleansing your face too often won't clear acne faster. On the other hand, cleansing your face twice a day just isn't enough to clear up acne either. To get acne under control, you will need an acne treatment product - an over-the-counter one or a medication from your doctor.
Consider your twice-daily cleansing a part of your complete acne treatment routine.