i think that Specialized P24AM is overpriced ($550) for what you get. a hi-tensile steel frame !?
in previous years, the P24 was about the same price, but with chromoly. so, they downgraded quality but kept the same price. weak.
your best bet is used on craigslist. pay attention to which bmx 24"s are all chromoly frame and fork, compared to which ones are hi-ten. something like a DK Cygnus 24" you can get for $150 used. and they have all-chromoly frame and chromoly fork.
the geo could be more progressive for park/street riding (i.e. the higher bottom bracket, like the Sunday Model C, Liquid Feeback 24", Specialized P24, We The People Avenger 24, etc. but at the same time if you're just wanting to get on 24"s... the geo on the DK Cygnus will be fine for dirt, although it could be a tad short in the front if you're tall.... http://shop.dkbicycles.com/DK-Cygnus-Trans-Red-Black/dp/B006BEFL4O
I agree with cmc. The DK Cygnus is a solid 24 that won't break your bank. I own one and it has been a great bike for me. As stated though, if you're tall (I am at 6'3") then it will feel a litle cramped, but it's very much not a deal breaker. Just make sure you replace the sinngle wall rims that it comes with. I also replaced the bars with something bigger, but that was my own personal preference. Oh, and I changed up the gearing. It was too easy to pedal so I made it a little more stout. I found mine used on Craigslist for $100 about 2 years ago.
honestly i never have any suggestions for bmx bikes under $300 anymore. they all come with inherent shortcomings that people will suggest to upgrade. and if you dont do those upgrades, you will pay in replacing parts very quickly.