Driving with Red Triangle--OK to use CD player?

I first read your post and thought a teenager wrote this, but then looked at your profile and saw you are a grown adult.

I think the last thing you would worry about the the CD/radio. The radio functions has nothing to do with the red triangle and won't make things worse. The red triangle is a fault that can definitely disable your car if you have an hour drive. The non blinking check engine light shouldn't be an issue if it's not blinking.

If you have to drive it without checking it through, make sure you have the basics checked. Your oil level is normal and not low, there is enough coolant in the radiator (remove the radiator cap to check), don't just look at the radiator reservoir. Make sure the brakes feel ok and it stops the car without any problems.

One of the more common issues with the Prius is the inverter pump failing, that's used to cool the electric motor in the car. If that fails, you may not want to drive 1 hour as it may overheat the motor. You can check if the pump is working by turning your car on and get it to READY mode. Then open the inverter reservoir cap to see if the coolant inside is pumping/agitating. If there is no movement in the inverter coolant reservoir coolant, that would mean the pump has failed and most likely the cause of the red triangle.

 

And I think that his thought is perfectly reasonable, especially if he has any experience with a failing electrical system on a conventional car.

Even though the odds are that a little bit of electrical usage from the accessories or A/C will not cause it to die on the road.......
Limiting the electrical usage is not a BAD idea in any way.
He might be the one in a million case where it actually makes a difference.