In the US it is customary to stay in the right lane unless overtaking, though this general rule is usually ignored. However as good law-abiding tourists we would tend to follow the rule. Keep a very careful eye on the overhead directional signs. If the lane in which you are driving has a yellow background then you are in a This lane must exit lane. Be aware of this situation because you must either change lane quickly or leave the freeway at the next exit - your lane will leave the freeway.
Lane discipline is practically non-existent.
It is essential, therefore, to watch both left and right mirrors to see who is overtaking, and from which side. Speed limits vary tremendously. The signs are black lettering on a white background. This would be, typically, 35mph for the lower limit and 45 mph for the upper. Whilst considering school speed limits it is appropriate to mention school buses.