The toll violation notice I have just received has prompted me to post this information.
There are a number of state roads in Orange County which are toll roads and they have just moved to a system where you can no longer pay cash at a toll booth. For international tourists this is a bit of a nightmare. You have to go online within 48 hours of using a toll road to pay the toll but the website does not accept non-US addresses or telephone numbers. I had to resolve this by paying over the telephone but these same issues arose and it took a 35 minute international call to deal with something that should have been simple.
It is worth international tourists trying to set up an account before they leave home so that you can just log in an add your licence plate details once you arrive. Then you don't need to got through the hassle of calling to pay your toll each time.