Where do you live? I live in southern California and I don't think they would work well here. I know a few people have tried them but I don't know of any gardens started by bombing an area locally. If you get good rain going into the spring where you live I think they could work well. But if you're in a drier climate I think you'll have a tuff time. I think local wildflowers seeds would be your best bet. But again, the rain make all the difference. In the local deserts it can be years between wildflower blooms.
I live in North Carolina, zone 7a
Rainfall for Charlotte NC
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
CHARLOTTE, NC 3.71 3.84 4.43 2.68 3.82 3.39 3.92 3.73 3.50 3.36 3.23 3.48