In Guitar Pro 6 you have the ability to export MIDI files. With a GP6 file loaded, export it as MIDI. Then simply drag it into a new open GarageBand project. Done.
You will have to fiddle with things like time sig etc, but everything should be in tact with the properly assign software instruments.
Thanks for taking the time to reply. My apologies, I should have been clearer... I realize that GuitarPro can export in midi format (and from midi to GarageBand import). I was trying to avoid the $59.99 investment just to use the software as a way to convert files.
Do you know of any software conversion products that bridge the gap for a lesser investment?