I am a claims adjuster(stop swearing at me, everybody! it's a living!
..) and I agree that you should contact Progressvie to ask about your specifc state laws. Here in FL, you can take out your own policy while living with someone else, & then drop yourself off your parent's policy, having them list you as an excluded driver, which means basically any loss you are in while drivign your parents cars would not pay for their vehicle's damages at all. So, if you do this, do not drive their cars at all.
lastly, if you change to Progressive, try to stay with them as long as you can. Ins co's make a profit after 7 years on average & it is then you can start getting some discounts on your policy...they like to take care of their long-term policyholders.
Good luck & let us know what they tell you!
Later!
Sean