My boyfriend cheated so we broke up but want to get back together can he change?

So basically, my now ex boyfreind got high and drunk because he got chucked out of his house and slept at a freinds house and cheated 3 times. i found out and he admitted to it. i told him that i cant see him anymore and that in a month time we should review the situation. i still love him and he wants me back. he has sent letters and flowers almost everyday. we both want to get back together but in order for that to happen he needs to change. he is telling everyone he will. but lots of people are saying he will never change and once a cheater always a cheater.. can he change? and if we got back would he cheat again? would getting back together be a good or bad idea? help.