Next year try an Earth Box....self watering...keeps the soil moist and cool. This is the first year I am trying them. Last year I used 5 gal buckets but the heat was too much for them. They needed watering 2 x a day at least. I think I may have over watered too...hard to keep a potting soil mix propery moist. Try using Al's soiless mix in the buckets. I'm sure it will preform far better than potting soil. Of course your plants are well established so the only option may be to mulch or scrape away a bit of the top soil and add Al's mix...the more the better. You prolly still have to water 2 x a day if it is really hot but the toms will love you...just don't over do the watering.

squibt

Instead of the Earthbox, try the Gardener Supply Self Watering Container (it's sold bundled with other stuff as the tomato success kit, but save the money and just get the container).

Only reason I recomend it over Earthbox for tomatos is the reservoir is larger on the GS box and Earthboxes typically require watering 2x daily with 2 large tomatos at summer's peak. The GS box generally once.

One area homemade self watering containers potentially outperform commercial units with tomatos is a larger water reservoir. A large tomato plant consumes up to 2 gallons of water per day at it's peak. That's a lot of water.

The one thing you never want to happen with tomatos is having them run out of water. This leads to blossom end rot, cracking, splitting and off taste.

I agree, to a point, with the earthbox suggestions. I live south of you in Fresno (it was 104 last week). I'm growing tomatoes in containers with water reservoirs using the earthbox technique, and eggplants in real earthboxes. The plants are huge and the harvest started a couple weeks ago. They take a nearly unbelievably large amount of water. I water at least 3 times a day.

I haven't figured out a good automatic watering system for containers in our hot dry climate. In your situation (preparing to move) I'd suggest putting them in a kiddie wading pool and flooding them.
-Hal

On the advice here & after reading a lot about Earth boxes, I made one just to see the results. Not quite recommended to transplant 2 4-5' tomato plants with cages but I made due. I used rather deep containers so the reservoir would hold more water. I had to rig the cover on the top so that strips of plastic were weaved in & around the cages. After a week I'm pretty darn pleased with the results. It's not been extremely hot here this week, just in the 90's, but I'm only filling the E-box reservoir once a day and still watering twice a day with the plants in regular containers. The regular container plants are still wilting between waterings but the E-box ones are nice & full. I'm planning on making quite a few more E-boxes & tranplanting all of my container tomatoes & maybe some squash.
While we've had sungold & blackcherry tomatoes for a month now, this past weekend we harvested the first 3 regular sized tomatoes! The weather this year has just been perfect for my veggies & it's still early. :)