My brothers back garden is very dry and sandy, yet he has a huge gunnera which thrives there. I can only think the gunnera's read no gardening books! If you can start your garden from cuttings and seed from friends and neighbours, in the same area, they'll be likely to have similar soil, also you won't loose any money if you've not paid for the plants! You'll be more inclined to experiment so you can just bung plants and let them get on with it.