Hi Nicole,
You can notch now or as soon as growth begins. This thread tells a lot: When to notch a tree
A less expensive way to deal with deer is to have a guard dog near your tree at night when deer typically roam. A Black and Tan or blue tick hound would do the trick. When I was a kid growing up in TN, I coon hunted with friends that had hounds. They love to track and chase deer. You can also go to the members map to see if you have others near you that have innovative ideas to manage deer.
Dennis