If your coming off a standard `1/2" hose bibb or whatever kind of valve you have, your already restricted to the number of sprinklers you can run. Before you install all this pipe in the ground and find out later that the heads only fizzle, why don't you try the heads your buying above ground first?
There are a myriad of different sprinklers on the market. Some put out as little as less than 1 gallon per hour to 35 gallons per minute. You should probably get a gauge to see if you even have enough pressure to operate sprinklers reliably. Not all city water pressure is the same.
If your yard is only 15 X 15, you could probably use shrub heads. They don't use much water, come in popup and regular and four of them would probably do the whole yard if placed properly.