Yeah dude experienced boxers punch without gloves can kill.....I guess the best method is if you get jumped punch few of em and run away.
A 4 foot 9 guy that spend his time training in the gym and train properly and lives the life is going to be better than the tall guy that trains average
Joint locks work better for a short guy. They are absolute dynamite against big people, because their longer reach just gives you a longer lever to use against them. I am 5' 5'' and if you let me get hold of your wrist, you are pretty much buggered. It also has the advantage that you can avoid doing too much damage to the other guy, hence no legal repercussions. Having said that boxing can be a useful addition to your repertoire. It's main advantage is that it allows you to strike without giving up your footing, which makes it very useful when outnumbered.
Some honest advice in the replies but honest advice isn't always the best. Most fights not under rules start at very close range and very often go to the ground, someone else mentioned that in the replies. If you want to hear some advice from a veteran of many street fights search Geoff Thompson. He's a published veteran of working some of the toughest doors in the UK and his first advice is always avoid being in the situation, but this guy is ferocious and not a big guy at all. Watch some of his training videos and if you get chance to read one of his books "Watch my back" then I highly recommend it, along with "3 second fighter". He's also written many self help books. Search Geoff Thompson doorman or phrases like that and watch some of his videos.