I can only see one thing that you might do differently and you've already realized this. You have to tell these men up front about your situation. Explain to them from the start what they're about to get into. Give them that choice. This will also avoid you falling for someone that's only going to leave once they find the truth out.
I definately think you should write your love interest and explain things to him. Give him links to various poly sites to help him understand. Most people don't get us poly folk. They need a little help. My wife and I have been in the lifestyle for YEARS and only now is her family starting to actually get what it means to be Poly.
Give him a chance, and apologize for not telling him at the start. I hope that he realizes that this lifestyle can work out for him and you and this can be the start of a very succesful relationship. I wish you my best!
Live life to the fullest 'cause you never know if you're gonna wake up tomorrow!