10 days in Tokyo and meeting unlimited japanese girls and boys too....only ONE i spoke too is very well spoken in American-slang-English 

And she is back from Canada....hehehehe....

Others, nah...dont even bother they wanna speak to you...  

Of course some do, for example that famous female Japanese pro ping-pong player (whats her name? Ai-chan?) that lives and plays in China. There are after all 125 million Japanese. Just like some speak German, French etc.

But common? Definitely not.
There's a huge influx of Chinese immigrant workers in Japan, esp. in the last 5-8 years.
You can find them everywhere: most cooks, a lot of restaurant servers are Chinese.
To us, they look and sound like Japanese. But to the Japanese, they can always tell.
Accent different, dress different, mannerisms different. It is very hard to speak native Japanese to the level that Japanese cannot tell.
One big giveaway is that foreigners cannot master keigo, which is the polite form of Japanese. You may know the words but very hard to know the context in which you must use which form of keigo.

Also, Taiwan (and Korea) were colonies of Japan for more than 50 years. Taiwan is the only East Asian country that does not hate the Japanese.

Very unlikely. Japanese are "book and exam smart" in English but cannot communicate effectively.
I've a couple of friends who graduated from Sophia University (the top English language university) and they are nowhere near native-level.
Most likely you stumbled upon either
a) kikokushijo - Japanese that spent childhood in a foreign country because of expat parents e.g. Utada Hikaru
b) they attend international school in Japan

No la...what i mean is...it's very rare to find a Nihon can speak English fluently in japan..

Zoakies relatives is Japanese...last year met him in Tokyo bring him around, luckily not follow the cosplay gurl to her house huahahhaah!