I think this slang "I am good" was originated from the ghetto in the US. I do not want to be seen as a person of that class. If my above-mentioned friend did not understand what it means that seems it is not a commonly acceptable slang. So if you talk to people you know for the first time, I would not recommend you to use that. You don't want to give a wrong impression to the listener.
You may argue that you hear Americans say that a lot and you just want to impress on the listeners. When I was in the US, sometimes when I asked my friends "how are you?" or "how are you doing?" (the latter is the American way), sometimes they would answer "I feel like sh...粪, It is perfectly alright to say that if you know the other person well. However, I would not recommend you to use that on people you know casually through the language learning web site.
Returning to the slang "I am good." If the listener does not understand this, he may think you mean that you want to say you are a good guy or you are not a bad guy. If you like to show off your English language skill and feel answering "I am fine" too boring or mundane, you may try "I am feeling good", "I am doing well" or "I am well".
我一个中国朋友问"I am good"是什么意思， 我经常碰到这样的一个短语或俚语，很多时我问我的同胞"how are you?"，他们有些时候答我"I am good". 我知道他们的意思是"I am fine"， 老实说我不大喜欢对方这样回答，正如任何俚语都是反映有关人士的级别，
你可能认为你听到很多美国人都是这样说，你想表演一下，我想说我在美国的时候问对方"how are you?" 或 "how are you doing?" (后者是美国常用），他们有时会答"I feel like sh...." (我感觉似粪)，这样的答法在熟悉的朋友上是无问题的，但你不可用于你认识不深的语言社交网的朋友。
现在再重谈"I am good"， 如果听者听不懂他可能以为你说你是好人不是坏人，如果你要炫耀你的英文语言能力及认为"I am fine"太闷太死板，我提议你用"I am feeling good", "I am doing well" 或 "I am well"