I agree fully with 185s sentiments. I would only recommend flying in the morning out west during that time of year. In the afternoon, fling is comparable to being thrown in a dryer with a brick. I did a similar trip to what you are planning, it was great and learnt a lot. make sure you call about fuel availability and carry different fuel/credit cards. Try to not rely on the GPS and develop your map reading skills. Also, drop into the areoclubs out there and say hi, there is a wealth of knowledge and experience (most are really nice people who are happy to have a chat) in those places.
Enjoy the flight,
Cheers,
F d