Where can I find Super GT?

Look in Las Venturas. I see them mostly there.

Go to second island once you unlock it. Then go to the driving school's parking lot. It's on the far corner

It appears in SF. When you beat driving school it is there. And it is always in the SF Airport, under the control towers, where the two helicopters spawn, it may be locked however.

There's no shortage of them in Los Santos- try the western part of the city near Burger Shot.

Around Rodeo,Pr!ckle Pine, and The Strip in Las Venturas.
Or just try any upper-class neighborhood.

San fierro airport, look around, its there.

Try getting it from the Export/Import board.

Ya usewayly there is 1 under the control tower in the san fierro airport. There a bullet or speed or gt by the tracks somewhere by the airport there are train tracks with a small place with a couple brown buildings 1 has a arck big enogh 4 a car 2 drive throght it is on ur right when u get throght the arch.Hope i helped.

You'll definitely have to wait until island 2

There is no easy way to get it. You could take a tractor into the airport in SF and tow it to your garage if it's locked, or grab a chainsaw and break of it's door at SF airport. If you completed driving school just go there.

use this map as a reference

http://img56.imageshack.us/my.php?image=gtasasupergtwm3.png

You will need to be far in the game, reach the next island.
Spawns at Driving School in San Fierro if you get all Bronze for twelve tests.