1 to 9, 14, 16 and 17 are outputs
10 to 13 and 15 are inputs
You can use whatever you wish within these constraints UNLESS your breakout board has some predefined pins that must be used for a certain function, most don't have that however.
Hood
Edit
Just as an added bit of info, the above only relates to Port 1, if you have a second port you can opt to have pins 2-9 as inputs in addition to the normal inputs.