Zinia,

First, you don't Ever need to till in the soybeans, or any cover crop. When the time came that you wanted to plant some veggies there, you could just trample them flat and start covering them with grass clippings. If you can get only a limited amount of grass clippings at a time, you can lay down some newspapes first (don't use the slick parts with lots of color in them) and then cover them with just enough clippings to hide them. That lets you stretch a limited amount of grass clippings to cover a much larger area. And you don't need to cover the entire area all at once. Concentrate right around your plants first, with circles of mulch around them, then fill in the rest as the season progresses.
May I suggest something? From 34 years experience, I know that mulching produces spectacular results, far greater yields than other ways of gardening. (And it's cheaper and much less work to boot!) A guy in Michigan who has sandy soil also, just starting mulching this year. And he just can't believe how much more his plants are producing than they ever have in the past. So my suggestion is that you try reducing your "acreage," to plant less area, but mulch it, to see if you can get all the veggies you want from much less space? You could then convert some of your present garden area back to lawn, to produce more mulch for you.
There are two other things that would help you get more from less space. One is the wire shelf trellis I use for my tomatoes, bell peppers, and eggplants. Last year, my two bell peppers grew to nearly six feet and produced 85 and 92 peppers respecticvely. (This year has been the worst weather year for gardening since I began! Yields have been much poorer.)
The other thing is what I call "The Two Story Garden." It lets you grow things like peppers, eggplants, and bush squash on "the ground floor," and things like greenbeans, cukes, melons and other vining things on normally wasted space on "the second floor" above them. If you'd be interested, please e-mail me. I am "puter challenged" and have no idea how to post pics on these boards. If anyone could tell me, I'd appreciate it.

Check out these sites, I was just reading about this topic the other day. I think the combo of oats and rye is interesting (the U Mass link below) but I don't have any practical experience with this.

Cornell's trials, nice pictures and comments:
Cornell's Cover Crops

U Mass's Cover Crop Study

UCDavis' Extensive Cover Crops Database w/ cultural info

Thank you very much for the replies. When I get a break again, sure will enjoy trying these new ideas. The peppers raised in the 2-story structure appeal to me. Would love some really good tomatoes next year.
Zinia