I'm not very familiar with flower gardens, but I've been reading a lot about vegetable gardens, and have had my own vegetable garden for each of the past several years. Two good books I've been reading are "The Vegetable Gardener's Bible" and "Square Foot Gardening." Both use similar concepts of raised garden beds and wide rows, but vary in many other ways. I'm sure the concepts they apply to vegetable gardens would carry over well to flower gardens, too. As for exotic vegetables, I'm not sure what you had in mind, but both of these books cover a wide variety of vegetables.
Since you are new to gardening, I would suggest starting small, so you're not overwhelmed in your first year. You might even want to consider a "container" garden. This is something you can most likely do at home, so you don't have to travel to your great-aunt's house to tend your garden. There are several "self watering" planters available that will allow you to go a few days between watering. If time to tend the garden is a premium, you may wish to consider using them. Here are two that I know of:
The Garden Patch
EarthBox - Home (http://www.earthbox.com/index.php - broken link)
Not only do these containers provide a steady water and fertilizer supply, their suppliers provide a lot of useful growing information that makes using them quite easy. I've been using the Garden Patch boxes for several years with great results. They are easy to use, and make starting a garden relatively painless. They also make the process goof-proof, for the most part.
Now, to answer one of your other questions, yes it is a little late to get started, but that doesn't mean it's too late. The biggest concern you'll have is soil, because soil preparation can take months, if not years. If you use containers for your garden, you don't have to worry about preparing your garden's soil, because you'll be using packaged soil instead. If you decide not to use containers, but opt for the "square foot" method, you'll also be building your soil from packaged products. If you do try to use the ground where you'll be planting your garden, you'll most likely need to amend the soil with various additives. The various gardening books cover the required steps in much more detail.
The next thing you'll need to do is decide what you wish to grow. This is important because some plants are not frost tolerant. Those that aren't won't be able to be placed in the garden until after the last frost. Where I am, we probably haven't yet had our last frost, so there are things I can't yet put into my garden. When the time comes, I'll probably buy and plant potted plants so I can get a head start on the growing season.