Don't be afraid to bother people; just go for it.
If the racers are (or seem!) busy head to race control (where the timing computer/PA system probably is) and introduce yourself to whoever is running the day, they can then introduce you to some racers.
Don't worry if the first person isn't very chatty, like any hobby every club has chatty/quiet members and you'll get some great advice by the end of the day
