A lot of organic matter breaks down into acidic compounds. Around here, pine needles are abundant, and mulching with them will make for acidic soil over time. I'm not sure if you have a source of pine needles or similar organics, but no price beats free, and mulching has a lot of other benefits as well. I don't think regular leaves are quite as effective as pine, but given that you're in Florida, it makes me wonder if palm fronds would have a similar effect.
If you need a stronger, faster acidity boost, you can work a bit of aluminum sulfate into the soil surface. I find it pretty inexpensive at my local garden center, but I could see the cost adding up if you are farming large-scale. Since my soil is naturally acidic due to the decades (centuries?) of pine needles that have fed it, I only use it on acid-loving plants (blueberries), rather than the whole garden. Be careful with it - too much can easily burn plants, especially those that prefer a slightly alkaline soil, so I'd limit it to plants that you know suffer from the well water.
