When considering a self defense technique, you should spend your time learning simple moves that are powerful and flexible enough to be applied against several persons quickly.

Simple combat-style moves such as an open palm strike to the chin, applied with explosive quickness a few times, will afford you the time necessary to get away. There is no need for flashy high kicks or fancy footwork.

If you use your knee to a groin, lean your head slightly to the side. This will keep your head clear as your attacker responds by leaning forward.

Should you find yourself attacked, stay calm and think as the situation develops. When adrenaline kicks in, everything will seem to happen in slow motion. Since you are calm, and you do not panic, your mind will process thoughts quickly and it will seem like you have all day to decide on your reaction.
Another thing to remember, your skull is incredibly hard. Use it as a weapon against an attackers' face and/or collarbone.
Most "fights" are won before they start, and aggressors will back down if you maintain eye contact and are not intimidated by them. You won't look like a victim or easy target.
You might have only one possibility to defend yourself, do not lose it.