Deca by itself without some form of test is not a wise choice. My first cycle was deca @ 450mg/wk/10wks and although I gained nicely, the loss of libido/functioning I experienced towards the end and beyond was no laughing matter. Although I did recover, it was fairly difficult.
Do as the others suggested. If you're worried about hairloss just run a small dose of test cyp or enth @ 300mg/wk. Add a topical anti-androgen and cleanse your hair with nizoral shampoo.
If you're really concerned about preventing future hairloss, there are drugs such as propecia and avodart available. Just research these drugs thoroughly beforehand, and be aware of any possible sides before taking the plunge. You must make a commitment to them; in other words, you'd have to give them a year or so to judge their efficacy or lack thereof.