Roadtrip Chicago To San Fransisco. Options

[FromDk]

Hi all.
I have read through the forum, and think you have a nice forum.
Me and one of my friends have planned a trip to the U.S. in April-May 2012th Therefore, I would hear what tips and tricks you have because we have never been to America before.

We must start in the city of Chicago and end in San Francisco. We have 19 days to ride in.
We are from Europe (Denmark), so it's exciting to travel to the U.S..

I have following questions which I hope some will answer:

Which route should we take? We would like to visit St. Louis, Las Vegas, Grand Canyon, Los Angeles, also running with Highway 1 to San Francisco.
Is there anything you should be aware of when you book places for your RV?
We have rented through Cruise America, it is a good company?
Can you sleep for free at Wall-Mart parking lots?

I very much hope that some will take the time to answer the above.

[Jerry S.]

In regard to your question about the "driving culture": In general, American drivers tend to speed. However, the higher the speed limit, the fewer the speeders. For example, if the limit is 55mph, just about everybody does at least 60mph with many doing 70+. If the limit is 70mph or higher, few people speed. I think this is more a function of greater gas usage at higher speed than obeying the law. In your RV, I would avoid the higher speeds (65mph+) because of fuel usage. An extra gallon of gas every 100 miles may not sound like much, but over a 3,000 mile trip it could translate into an extra $100+ in gas costs.