The Western Express route starts in San Francisco. Where are you planning on starting?

Are you looking for a "short" route or a "safe" route. They usually aren't the same. Direct generally means interstates or other high traffic roads.

You will be crossing the desert and shouldn't simply mark off 75 miles for a day's ride without determining where your water and other services will be available.

For example, Hwy 50 across Nevada is on the Western Express route. This earlier thread talked about getting water on "the loneliest highway in America.".

Ray