Thanks everybody. This is great feedback. Exactly what I was looking for.
I should maybe tell that we are not looking for summer vacation but more for an experience for life and the possibilities to see more of this great country.
we have now lived in Houston for the last 2 years with hot weather and a pool in the back yard.
From April we will go back to Europe with very little chance of doing this again. We can't leave earlier due to my job. So this is our only chance.
We don't mind tempatures around 70'. Just that it is not frezziinnnggg cold al the time :-)
As a bonus we be ending the trip in Hawaii end of march out of LA.
We plan to drive to these points:
grand canyon-Mesa verde-petrified forest-las vegas-san diego-San Jose-Los Angeles-san fransisco. Not in that direction but just as an indicator. And then see how for north of San fransisco we can get :-)