I agree with Busskipper - for us to really help you we need more info. West Coast - OR/WA or swinging south and going to CA? The Coast is a long way along it and all kinds or variations depending on your wants.
And, for example, the best time to be on OR Coast is mid Aug to early Oct. But those are the best times to be in the mountains of WY or CO - and places in the mountains start closing down around mid Sept.
Fill us in - we are here to help.