Watering should always be as needed. Even with a sprinkler system installed at my house, I still have to adjust it for the season and rain. Right now my system is off and I only run it manually if we don't get some rainfall every week.
To mitigate moisture needs of your plants it is best to group your plants according to how much water they need. The ones that want to be evenly moist in one group, another group likes to be dried out between watering and others want to be in a puddle all of the time.
Add compost to your planting site at least 2-4 inches worked into the top 6-8 inches of soil. Compost will help hold on to water and apply a layer of mulch on top to reduce water loss from the surface. To use less water, run your drip irrigation under the mulch.
The type of soil you have, how windy, hot, rain, time of year, water requirements of the plants, and whether the pots are in containers will all make a difference on how much water is required.
The only way to do it is to test. Run your irrigation system till the soil is moist 4-6 inches deep. Dig several test holes to make sure the area is being evenly watered. You may have to adjust or add watering emitters/heads to the dry spots. Dig a test hole daily to determine your watering interval. Water again when your soil three inches deep is almost dry but before your plants start stressing. Some plants like tomatoes will wilt in the heat and others will curl their leaves but that is how they adapt to heat and drought. They should come back by evening. Most container plants will need to be watered daily especially if they are pot bound or have large plants in them. The closer you have planted the sooner you will need to water. Small plants can go longer than large plants with large root systems that are in fruit or flower. As the garden fills with mature plants the watering interval will decrease. During the cooler, wetter months you may be able to water twice a week in a garden that has mostly small plants with lots of organic matter and mulched soil that is more loamy not sandy.
If you have sandy soil, you will still need to water nearly every day.
When the weather gets warmer and the plants size up and start fruiting you may have to water daily or every other day.
The longer and deeper you water, the deeper the roots will go and the longer the plants will be able to tolerate a dry spell. So it is always better to water low and slow rather than quick and shallow.
Even if you automate the system and install a moisture meter. ( they do have it for lawns, it does not work well since the water in the meter does not always dry out at the same rate as the soil), you still need to look at the plants and adjust for conditions that change moisture levels like rain, heat, windy weather, type of soil, size and number of plants per square foot, and individual plant needs.
In the beginning it does take a while to get a hang of it, but after a while, you will be able to look at the plants and the top of the soil and tell if they need more or less water. If you are going on vacation and it is only for a week, and you have been watering twice a week, you can probably keep that same schedule, even if it rains while you are gone. Just make sure the water timer and batteries are working.
Happy gardening in Hawaii. Gardens are where people grow.