My cell phone service provider is Consumer Cellular, and I have signed up for international service for an upcoming trip. I am wondering if anyone has experience using Consumer Cellular in France. Other than using the available wifi, should I expect good, mediocre, poor, or horrible service? (I know there can be spotty, if any, service outside the cities.) Will I need to purchase a temporary cellphone?
Whatever subscription you have, it will use the French mobile networks.
So, except in a few remote areas in the middle of nowhere you wont have any problems with quality of service.
You don't need to buy another cellphone, you can have a prepaid SIM card (or E-SIM) with a French operator. As below with Orange (the largest in France)
https://boutique.orange.fr/vitrine/carte-prepayee-orange-holiday-europe-en/
It will certainly cost you less than the one you are talking about, from what I have read on this page:
https://www.consumercellular.com/help/international-rates/roaming
The MB of data costs between $0.06 and $0.23.
Which is equivalent to $60 to $230 for 1 GB
The cheapest prepaid SIM card offer from Orange, valid for 14 days, will cost you €20 for 12GB including 30 minutes calls + 200 text worldwide.
A peculiarity of the mobile phone industry is that when you're roaming your phone tends to connect to the strongest signal, no matter the provider.
This means that when you're in a different country you will often get better coverage than someone who lives in that country