Ask all the questions you want

In my local region, I'm the assistant to the Novice Chief, so I'm more than happy to help out.
Sometimes you will encounter those who feel that the added weight will ruin their times and thus take them out of the running. Those are not the people you want to ride with anyway.
Hopefully (and again, I can't speak for your region as it isn't even the SCCA, which I'm most familliar with), you will find those people who have been doing this for 20 years and for whom winning is just an added bonus. Those are the guys who are typically the best because they are out having fun and not taking everything so super seriously. If the event offers instructors, they are most likely the ones willing to bring you along (and for my SCCA region, it's technically only the instructors who are allowed to have people ride along... other people are required to get explicit permission from the safety chief).
Don't make the first thing you say to someone "Hey, nice car, can I ride along?" If you are being a proper novice you should be asking numerous questions as you go along from anyone who seems like they know what they are doing. After your secondish run, you should feel a little more comfortable with the people around you, and feel a little more comfortable popping the "big question." And if all else fails, find the person you registered with, teched with, or who did the novice walkthrough (if offered) and ask them if they know anyone who would be willing.
Honestly, I've never ever had a problem getting a ride along. I'm simply honest and upfront "Hey, I'm new to this autocrossing thing, and after having driven a run and seen your driving, I was wondering if I could possibly ride with you once? If you think I'll be a distraction, I completely understand and can try asking someone else."