Reddit mentions of Hedges and Hedgelaying: A Guide to Planting, Management and Conservation

Yes keeping the dear out can be tough, it really comes down to how hungry they are, and it only takes one browsing to really set a planting back, especially in the early stages. They'll prune all the growing points for you ;O Thats a really complex issue and the answers depend on what your overall project is.

I think if you just stay mindful of what might limit the Mimosa from being helpful, you'll be fine. It sounds like it wont be stressed in that situation. There are many other trailing legumes like that that you could mix in for good measure like alfalfa. Try several at once and see what thrives. Just remember an excess of N can cause pest and disease problems in overly-vigorous growth, in some cases.

Are you doing hugelculture (sp?) style beds?

Also, if you are trying to create stock-proof fencing you should read more about hedgelaying. I don't think anyone does this in north america but the results are second to none in terms of functionality. I own that book, its an exceptionally complete manual