I think you should water only when you need to.
With really deep, really good soil, you should be able to go the whole summer without watering.
Granted, the fertilizer can be expensive. But, I am suggesting that you not use much - you might get two or three years out of one bag. And I am gonna try and save you lots of time, water, etc.
Here is the cheapest I can find. You might be able to find something similar that is
local and cheaper. The key is: feather meal and organic.