They are typically ready to harvest around Labor Day.
Hops can give a dog a heart attack if they get into them. This is usually when the dog gets into them when you dump your trub after the boil, or if you use a hop sack.
When growing them, its best to clip the bottom few feet's worth of leaves leaving only a bare bine close to the ground. This will help keep insects as well as mold/fungus off the plants as they grow, and it will also keep the flowers out of the dog's reach. If your dog likes to chew on plants, you may want to put a chicken wire fence around them just to be sure.
First year they usually don't produce a lot. 2nd year they'll produce a lot more.
It's fun to brew with them, but the big issue is you really don't know what the %AA they are. You could end up with a beer that is over or under bittered if you try to use the as the only bittering hops in your beer. You will be more consistent if you bitter with a commercial hop and use the homegrown as flavor and aroma additions.
Also, if you fresh hop with them (ie, throw them in directly, without drying them out), they are approximately 5 times heavier than dried hops, so you have to mulitply your weight by 5. 1 oz of dried hops = 5 oz of fresh.
HTH-