Avocado Problem
The holes in the leaves could be attributed to a couple of things: insects and / or snails & slugs. Try to hunt for the critters after dark when they come out to feed and hand pick them off and dispose of them. You can use an organic snail bait such as Sluggo to curtail the snail & slug activity. If there is an insect problem of some type, the best thing to do would be to take this photo and a sample of the injury to your local garden center and see if they can suggest appropriate measures.
the other issue that I see is the browning of the leaves. This time of year, leaf tip burn is fairly common, and if it is due to salt burn, make sure there is adequate drainage around the tree. Avocados need excellent drainage (hillside is a good choice) and are very susceptible to root rots as well as salt burn from the alkaline tap water. Here's some helpful info: http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/avocados.html.
