I think staff at CSS will suggest tire pressures at the beginning of the day. If not, feel free to ask and you will get the best advice for those immediate conditions and for your bike. I assume this is your first level class, and in this case you will not be riding that aggressively, so don't worry about it. Set your pressure to mid 30's on both tires - you won't need higher than that. Once you know what's recommended, just let some air out - this way, you don't have to deal with adding air and needing a compressor.
Have fun and let us know how it went, what did you learn, etc.