Can I file JUST my federal return and not my State return via Turbo Tax

Yes, you can e-file your federal return (under the file tab you will file your federal first), and not file your state tax return with TurboTax. Just do not complete the file portion for the state (you can select print and mail in your return). 

Yes, I do it every year.  I e-file my federal tax, because t is included with price of software, and either mail or e-file on state own tax website.  15 years like this.

Yes, you do not need to file your state tax return with TurboTaax. You can just file your federal return. When you are in the file tab (once your return has been prepared), you can select to e-file your federal return (or print and mail), then your state options will pop up. You do not need to select e-file, most people will select print and mail, and then they do not print and mail in the return.