What spanish accent should a black person learn?

What does the fact that you´re black have to do with accents? You will have an american accent regardless of the accent you learn cause you´re a grown up, and you will never sound like a native speaker, I´m from Argentina and I speak with an americanish accent but I would never pass as a native speaker, we all have influences from our native languages that seep in every now and then.

If I were you I´d learn mexican Spanish since the US is full of them

You might want to mimic the Spanish accent, if you want to sound intellectual. Or a Mexican accent, if you want to sound native (assuming you live in the USA, and not in the UK).

These days you can learn how to speak Spanish over the internet. Check out this online course, it's voted as the best Spanish online course of all time: http://www.rocketlearner.com/spanish The course is very easy to follow, I was able to learn Spanish in just 3 months.

I live in New York City, I wanted to go to a Spanish language teacher but that would have cost me over $800 per month. Good thing with this internet, $800 it's a lot of money for me.