I used to ride there (way back when I lived in Mpls)-- it's an awesome track, and you should definitely go check it out.
They sometimes don't open until later than you would expect because of flooding in the tunnel under the track, but the best thing to do is call and/or email Bob Williams (contact info on the web page), the track director. He took over a little after I left, but he taught me to ride on the track. He's a very nice guy and very knowledgable and helpful.