Can the temp display be changed to Celsius from Fahrenheit on the 2008 Prius?

Correct. The change is made by changing the "country" code in the programming. You can select to change it if you get into the diagnostic menus, but nothing happens. At least one dealer also tried with the THHT (Toyota Hand Held Tool) with no joy.
But ask. It costs nothing to ask (usually). Maybe they'll call Toyota US and find a way.

 

The preferred system of measurement by federal statute (Acts of 1865, 1972, 1988 and others) makes SI, the modern metric system, the only legal system of measurement in the US. We have SI cars, guns, paper, money, skis, cigarettes, computers, computers and more. No one objects to being paid in "metric" money or driving "metric" vehicles. Effective 2010 all exports to Europe must be exclusively in SI units. It is a major oversite on Toyota's part to not allow a simple toggle to degrees Celsius. A software update for the MFD should correct the problem.

 

Anyone figured out how to change the MFD to show temperatures in Celsius, not Fahrenheit yet?

 

Back to the ORIGINAL question: The best way is to obtain a MFD from a wrecked canadian Prius. You can then sell your old MFD and probably break even.

 

I would love to be able to change mine over to all metric as well. When I had a 2010 Honda Insight, if I pushed the button to change to metric, the only thing that didn't change was the inside cabin temperature. Like I said I would love to change mine over to all Metric as well but it wasn't a deal breaker for me. I am assuming that someone will eventually figure out how to do it and post in on here or Toyota will update the programme for the computer. I would think it can be done now with the simple click of a mouse. But at the moment Toyota USA hasn't released how to do that.

 

Maybe you can put a conversion table on paper and stick it to somewhere on the dashboard. I probably will do that when I get mine.

 

Most newer BMWs you can very easily change to the method measure you want, I also own a BMW X3 and I can change all settings other then the odometer. Much nicer having the climate control in Celsius where it makes sense to me and most of the world.