Yes, you can, but be careful! Remember, that turkey breast is going to displace lots more oil than a couple of servings of fries, etc.
I know of several people who've deep-fried turkey breasts, pork roasts, etc. with their turkey fryers. They've all commented it takes longer per pound than doing a regular whole bone-in turkey. The turkey breast is solid, so it takes longer for the heat to penetrate to the center as opposed to a whole turkey with a large opening in its center.