I'd go with a 20" if i were you because thats the standard size I think, 24" is more for jump bikes (I think). And the kink curb 2011 is about $250 from action village, but if you can find the 2010 version I'd guess it will be closer to your price range, it was a bike I was looking at guetting and I was impressed with what it had to offer =D
hmm, if your 5'8'' you might be a bit too big for a 20 inch, but then again a 24 inch might be to big for you, go to a bmx store and sit on both see how you feel, you can always adjust a few things to fit you, and the bike from that amazon link looks pretty good
well if your just gonna do bmx get 20" , my friends 5ft 7 and hes fine on a 20" , ps are you good what can you do ? or are you just a starter ? also, ermm 24" is just a dirt jump rigid id say.