The finger test--stick your fingers in there--if they feel cool, there is still some moisture. If they don't, watering is overdue.

I have a Bay in a pot in full sun and water it almost every day. Most plants I have that get more than a couple hours of sun need water almost every day.

How big are the pots? In this climate, bigger is better due to how fast they dry out and how hot it gets. One pot inside another with air space between the two also helps keep the roots a little cooler than they otherwise would be.

Remember that more frequent watering means more frequent fertilizing as well.

Fall when we get the Santa Ana winds with temperatures in the 90s and humidity down to less than 10%, I need to water two or three times a day.

I don't grow much in pots any more. The ground is easier!

You did not mention the type of soil mix you are using. My standard practice on potted plants is to water weekly, flooding the potted plant sometimes twice if the mix is very porous.
For plants in your site I would move them into partial shade because they are in pots. Otherwise watering should probably be based upon how dry the soil mix is. Have you determined how heavy the pots feel after a thorough soaking? After knowing this you can determine just by lifting each pot if it needs water. For fast draining mixes you may want to water 2-3 times weekly during their growing periods.

If you are using a real container mix,(check out the container growing forum)you will not ever over water. You will need to fertilize regularly as each time you water, about 15 to 20% of the water applied will be seen to exit the container. You will not need to worry about a buildup of salts. Most full sun plants will do well in full sun in a container, some will need the container itself shaded. Al

INstead of sticking your finger in the soil, you can try using a wooden dowel. Stick it down as far as you can. I let mine sit for a few minutes, go do something else in the garden, then come back and pull it out. If it is cool and moist, don't water. If it's dry, time to water. I bought dowels at the hardware store (OSH), then cut them into the lengths I wanted. It's good to have several so you can test several containers at the same time.

For clay/terra cottage pots in all day sun, you are also losing a considerable amount of water through the sides of the pot. I think you have already surmised that you are both underwatering and underfertilizing your plants in our year round growing conditions. I prefer to use larger glazed pots for full sun locations to reduce water loss, and also prefer to connect containers with automatic drip irrigation. During summer in full sun, I typically water every day for 3 to 5 minutes, and if this is too much at one time,I might split it into a morning and afternoon watering. If your plants aren't growing much and show signs of moisture stress, you might try larger pots, more watering more frequently,and using both a time release fertilizer in combination with periodic liquid feeding. Or move them into less sun... pots with less water needy plants may be an option if you don't like daily watering. Succulents such as agaves, aloes,aeoniums,echeverias, etc work well. Many supposedly drought tolerant plants like California natives don't accept the same low watering frequencies of succulents, as they dry out just as quickly as normal plants with a limited root run of containers.__