Yeah... the daughter and I have been there several times (it's real close).
The vet track is very tame so we spend most of our time there. The quad track is mellow as well, so we go there when the vet track is being watered (and for a change of pace).
The main track isn't too bad (for difficulty), but there are too many fast guys doing bigger jumps. I don't want to get run over.
The main pain is the 25$ per year membership fee and the 25$ entrance fee.
We haven't been there in while, but in the past, the schedule was bikes only on the quad track on Sundays, so it was a good day to go. I believe it was quads only on the quad track on Saturday. The schedule may have changed, so you need to check it out or phone. Link below -
http://www.milestonemx.com/
If you plan on going at night (it's getting hot), you might want to check which tracks are lit. The vet track was not lit in the past - I'm not sure about the quad track.