Exactly - I've lived in AZ, FL, and spent a lot of time in SoCal. There is plenty of sun in those places.
If you can generate solar power 80% of daylight hours, that's a pretty good place to start.
Again, it's not an end-all-be-all solution. But you're talking about some very highly populated areas that could be using solar energy a hell of a lot more than they are now. Phoenix, Tucson, San Antonio, Dallas, LA, San Diego, Houston, Miami, Orlando, Las Vegas....that's a lot of places that could be utilizing solar power in a way that does move the needle. That's some 30-50 million people (if not slightly more) that could reduce their use of the federal grid in a measurable way.