[breadfan]

The scene on SEA is VERY zerg heavy. So if you are a fan of ZvZ , you're in luck!

Terran is next most common at the highest level, but very scarce in lower levels, whereas protoss is less seen at the top, but very common in lower levels.

I don't know what sort of info you really need - I don't want to assume you have 0 knowledge and I only played BW many many years ago.

Brief description:

Zerg = Heaviest macro, not much micro required comparatively
Protoss = The opposite of Zerg - simplest macro but the most micro intensive, also they are generally unkillable which is a nice quality if you like winning
Terran = a mix of the two with a lot of versatility in play style, they are more a jack of all trades (good at everything, amazing at something). Easy (easiest?) to learn, but the most difficult to master

Honestly, I think just pick one you are interested in playing. Whichever you choose, you will have that learning curve as you adjust to the new game mechanics, it will all end up the same