Ok the last gt game ive ever played was gt2 and I liked it. I know the gt5p is not the whole game but is it worth 40 dollars? Also I thought moterstorm 2 was also good, should I buy that instead?

I would say wait for GT 5 which will arrive towards the end of this year and it will offer all GT 5 P has plus much, much more in regards to cars and tracks.
If you want to play GT 5 P rent it from your game store. If you like it, GT 5 P can be found for much cheaper than $40, second hand copies of it should be widely available from your game store at a cost of around $20 to $25.
GT 5 P has only 70 cars and only 6 tracks plus online mode and completing this game will count towards GT 5 game progress when you finally get that in the near future.

Motorstorm 2 is better.

Yes its worth your money.

Thanks..and one more question can you download the gt hd demo still?

Wait, you have a PS3?

 Yep, I got one a few days ago...

Dude thats suck a damn waste.

Go with Burnout: Paradise. Its a FULL GAME with all the DLC.

I find GT5P fucking ridiculous imo. Dunno why anyone would want that game.

 I didnt like burnout...didnt like the demo anyways.

=/
If thats the case just wait out for the official version. My friend likes GRID. Maybe that?