When can I cut down and clean up my garden for fall?

Depends on area. I am outside Philly, Pa and try to hold off on the bulbs till end of October.

Where do you live? Where I am we will not see cooler weather for quite some time. Now my friends in the middle of the country and east coasters already are feeling fall like weather. Here is a link to find your zone and helpful info for your area. Enjoy the season!

http://planthardiness.ars.usda.gov/PHZMWeb/

Not too early. Clean out all plants that are finished blooming and cut others back drastically. Plant bulbs and put down pine straw or mulch. You're ready for spring!

The minute you get tired of it. If you are done for the year, start cleanup

perfect time between now and end of October