If I was cutting through a racecourse, I would give way to everyone and try to keep from feeding someone dirty air. Otherwise, just go around. You don't have to, but it would be the polite thing to do. The racers probably won't notice, but if you call 'starboard' on them and you're not racing, you can bet you're going to get a stink eye from the racing crew.
Merit 25 # 764 "Audrey"