My first suggestion would be to find a plant-sitter lol :)

However, since that isn't fesable, how are you traveling? If it's by car, you could possibly start some seedlings about 4 weeks or so before you go, and take them with you, that way they would be ready to plant by the time you got back. (for veggies, you would have to make sure that they would have enough time to ripen before your first frost.)

You can also sometimes find plants already growing (vegitables and flowers) at nursurys and places like Home Depot and Lowes. In fact, the Lowes near me already has plants lioke broccoli and cauliflower ready to be planted. You could ask around and find out what they plan to have avalable in mid june. They will be more expensive that way of course, but if the alternative is having nothing, I personally would go ahead and pay the extra lol.

Barring that, I really don't know. (I'm fairly new at this too!) You might ask in the vegitable forum about fast-growing veggies.

Just buy your plants in June. The garden centers usually have them up till July. By then the plants at the garden center will have gotten bigger, so they've actually been growing them for you while you're away. I don't see any way for you to plant things before you leave. Unless you can do a wick watering system for your plants. Wicking could last awhile, but maybe not a whole month.