Congratulations on this special milestone in your child's education!
The cut-off dates for enrolling in kindergarten vary by district and school, so to get the most accurate answer to your question, I recommend you contact the district and/or school your child would attend. If you don't have their contact info handy, you can use SchoolFinder to research it: http://www.education.com/schoolfinder/
It's possible your child will have to wait until Fall 2010 to enroll, and that may be better timing for him (developmentally and academically). Here is a related info center on Education.com you might review to learn more: http://www.education.com/topic/kindergarten-readiness/
In the meantime, consider doing learning activities and worksheets with him at home. Here are links to free resources on Education.com to support you in this endeavor:
It all varies by the school distict. But usually if your child will be 5 y/o by December the first of that school year they will let them enter for that year if after then h/she will have to wait untill the next school year. As for now you can still look for Pre-schools that your child can enter for now to prepare him/her for the up and coming year.