Dont worry about amending for the trees. Their roots are going to go far deeper then your could ever effect the PH of. Just search this web site for blueberries and soil and you will find tons of posts on what to do to make em happy. I would simply work the soil directly where the blueberries are to grow.

What about our hard water? I've read some other posts where people hand-water their plants with vinegar-spiked water.

I was kind of thinking of taking some fat (wide) 15 gallon tubs, cutting out the bottoms, and using those to plant the blueberries inground. That way, they would be somewhat isolated and I could treat their soil more locally (iron sulfate, elemental surful, peat, and some of the other amendments that people have mentioned in other posts). Maybe it would be easier to keep their immediate environment more acidic if I was treating a smaller area? How does that sound? Do you think doing that buys me anything?

I don't know what I could do about watering though... seems the hard water would be fighting my attempts with the soil...

That would probably help your attempts Caligardener. Or you could just grow it in the big pots. Blueberries are known for shallow roots and so they might not grow out from under the bottom of the pots anyhow. I read a post today about storing rainwater for watering blueberries. That sounded like a great solution to me. I think I'll try that next year. This year I would have an empty barrel anyway, with the lack of rain.

I didn't think anyone else had a wax jambu. I did a similar planting one year ago. I'm further inland, but my experience is that a mango and loquat took off right away, but the wax jambu dropped all its leaves and looked like a dead stick for the first six months. Then it suddenly took off and is doing well. A lychee planted at same time hasn't changed much for a year, and a longan suddenly died for no apparent reason.

I've been eyeing blueberries also...and plan on building up some dirt berms to plant them on. That way I can affect the ph easier if needed.

I live in South Orange County. The raining season here is from January through May. Last December, I bought a 24" box Loquat tree with fruit on it. Just recently noticed that all the leaves are wilted and burned on the edges. Even the new leaf sprouts look the same. Can anyone tell me the possible cause? Is it too much watering or too little? Is it Fireblight? If so, should I use Bromide Spray?

You might want to contact the California Rare Fruit Growers with these questions. THey have 2 branches in San Diego County. Also, there is a very nice Sub-Tropical Fruit Garden at Quail Botanical Gardens in Encinitas, probably they have some info that could be helpful to you. I've had luck growing blueberries in pots with acidic soil amendments.

Here is a link that might be useful: California Rare Fruit Growers