It depends on the motivation, strength, and intelligence of the attackers....
Notice, I say attackers. I wouldn't kick any guys asses if I can avoid the fight.
If it's 2 on 1, my first shot has to stop 1 of the attackers... then it's 1 on 1 and I have a chance.
If my first shot doesn't succeed, I'm going to be in trouble.
If there are more than 2, it comes down to luck.
Knowing martial arts helps (Tae Kwon Do)
But, it helps your confidence more than anything...
If they get me on the ground and pile on top of me, I'm doomed.
But, if one leads the attack, I'll attempt to take him out with as brutal of a kick as possible (maybe a really hard back kick to the sternum- should knock him back quite a ways). Then my attitude and attacker's motivation really comes into play. If I can stand there and say something like "okay, 5 on 1 was even, but now it's 4 on 1... are you guys sure you want to put yourselves through this?" I cross my fingers that they back down.
(I doubt I can surprise them again with a similar kick. If they don't back down, I'm screwed)
It's funny... the people who've taken martial arts know that it won't really help a whole heckuva lot in a street fight.... an initial advantage, especially if your opponent(s) don't expect a few things...
But, people who haven't taken martial arts more often seem to think that it emparts a huge advantage, thus the confidence (or pretending to be confident) will possibly make them back down instead of fighting (when you don't have control to avoid the fight... cornered or something).
When taking lessons in college, I was stopped by 4 or 5 big football players while they made fun of my uniform (I washed it in hot water, and it shrunk, going only halfway down from my knee to ankle. Semi-jokingly, I kicked the baseball cap off one of the players... 5 big football players were instantly intimidated by me. They could have kicked my a** in a heartbeat if they wanted to, but didn't know it.