Heard through the grapevine your interested in Independence Parks, check this one out it would be perfect. I have done practice for years here. If you want any help with it give me a holler.
The Masters 35+B (Cat 4 only) and Master's 45+B (Cat 4 only) would be a good class to start with. We added these classes because about 1/2 the Cat 4 field were 35 or older. I don't know how old you are, but I think you would do well in the Masters B class. You are riding with other riders your age and you don't have all the "sandbaggers" that typically race the 4's :-)