I would suggest you drive down the Coast of California - staying in Carmel/Monterrey or Big Sur (3 to 4 hours from SF) for a night or two - and also tour Hearst Castle.

You might even visit some wineries along the way (Paso Robles, Cambria, Solvang/Santa Ynez Valley) - and finish up in LA - another 4 to 5 hours from Hearst Castle/San Simeon.

Then from LA - fly to DC - or drive to Las Vegas (4 hours) to see it for a day/two - and fly to DC from there.

And for some mini-trips - you could also drive up to beautiful Lake Tahoe for a couple of days - or to Yosemite, both about 4 hours from SF unless it's on a Friday afternoon going - or returning on a Sunday.

Another option is to drive to the Utah border from Las Vegas (2 hours or so) - and then you are close to the Canyons east of there (Bryce/Zion) - or take a day tour from Vegas to see the Grand Canyon (you could also drive it - 5 hours) - or take a helicopter tour from Vegas.

Utah and Colorado - as well as other western states are beautiful to drive - but they are a distance - even by Aussie standards.

Tomsd, Thanks for the suggestions my husband thinks it will be too hot for us to really enjoy.

Where could we go to escape the heat of Las Vegas? previosly spent a month in Reno, NV in August & it was HOT!!! Loved Lake Tahoe it is so beautiful, went to a couple of outdoor concerts on the Lake just magic backdrop at Sunset.

The only place in the US you can be fairly certain it won't be hot in July is San Francisco.

If I understand correctly, you will arrive in SF and have 12 days before you have to be in DC where you will stay for 3 weeks and then return to SF area for 2 months? If so, seems you will have lots of time to do CA/regional short road trips (Yosemite, wine country, coastal highway, Tahoe, etc etc) once you get back to SF?

Also sounds like you haven't yet seen anything in the middle of America AND you don't want the high heat of places further south like Vegas so to me, it seems pretty clear cut - go to one or more of our beautiful national parks such as Yellowstone, Grand Tetons, Rocky Mountain National Park, etc! The weather will be nice but not crazy hot and the Rocky mountains are gorgeoous! For example, you can drive from SF to Jackson Hole, Wyoming in 2 days 1 night and then tour around Grand Teton National Park and Yellowstone for a week or so and then drive to an airline hub such as Salt Lake City and catch a flight to DC. I say Salt Lake City just because it is likely you can get a direct flight to DC for a reasonable cost - the local airports in Jackson WY, Billings, MT, Bozeman, MT etc might be more convenient options depending on where you go but they also typically are more expensive (as there won't be direct flights) so check your options....