Hi
I'm coming from Ireland to do a US Roadtrip in October and I have a few questions
I'm going to route from San Francisco along I80 to Cheyenne and then go down to Denver for a few days. Then to Las Vegas before heading towards the Grand Canyon and accross to Hilton Head.
Questions
What are the speed limits, I have heqard out west on the Interstates it is quite high.
Are there frequent gas stations, should I carry extra gas?

Thanks