I agree with the other folks that said it is best to learn under lower pressure conditions than when you know you have to transport yourself across hundreds (thousands?) of miles before you can take a long break. That said, I think you will find the insight’s manual transmission easier to drive than whatever other car you may find to gain experience on. Mostly this is due to the insight’s light weight. It is relatively easy to get up to an adequate speed for first gear, so it is fairly forgiving of less than optimum throttle/clutch coordination.
3 other ways to grind gears: Shifting while forgetting to use the clutch, shifting without the clutch being completely depressed, and inadvertently trying to put the car into reverse when you meant 4th. Although grinding gears is not a good thing it is not the end of the world. You will do it sooner or later. Just don’t make a habit of it.
“Burning the clutch” is another neophyte pitfall, although it is not such a problem with the insight’s light weight. Just don’t make a habit of making smooth first gear starts by revving the engine and letting the clutch out sloooooowly (let it out only moderately slowly while bringing the engine up to speed. You’ll get the hang of it). A burnt clutch smells like burnt brakes.
Be patient with yourself! Learning the finer points of high mpg takes a while and will come as you get more confident with the transmission.
Don’t worry about the shift indicator arrows at first. They are only guidelines for optimum mileage. They don’t know as much as you know about the upcoming conditions and you won’t hurt anything by letting your RPMs get higher than those lights want to let you. If you try to follow them you will find yourself making too many needless (and inappropriate) shifts.
Expect to have to downshift to 4th or even 3rd to get much power at freeway speeds.
Have a good adventure! Once you get out of L.A. the hard part should be over!