It's not muddy,at least on that day.You have to be aware of where you are in relation to the bikes.There are places where you will be pelted by the dirt/rocks/debris.This particular shot is of professional racers on a well prepared track.However it is a grassroots type of family sport on the amateur level.Entrance fees for those races is about $10 USD and they everywhere every weekend 'year round in most of the US.It's a pretty dynamic activity and you're free to wander around the track (usually 1-2 miles in length) for different vantage points,shade or comfort.They start early in the morning with practice and and are usually over by 5-6 PM.
You will need to be careful with the camera/lenses but it's not unduly hazardous.
And here's the shot as it came from the camera.
And another for grins.Same track,a year later.