Research this VERY carefully, and per the laws in your State:
For example:
http://singleparents.about.com/od/legalissues/f/unwed_mot...
http://answers.google.com/answers/threadview?id=438245
http://www.ehow.com/about_###-###-####_father_s-child_s-l...
http://answers.yahoo.com/question/index?qid=2010101312305...
http://freelawanswer.com/law/2296-1-law-1.html
http://wiki.answers.com/Q/FAQ/628
I would... also look into getting an Attorney... you will need one, eventually...
Key thing to remember, he may 'sign' the certificate... but that is not saying you HAVE TO give your baby HIS last name.
2 different things.
And you are not married to him...
And even if he is saying 'now'... that he wants to be there for baby... chances are.... he will not. Many men, married or not... change their minds, once 'reality' sets in. Or they are only responsible... only when it suits their mood.
And when/if your baby's Daddy... gets another new girlfriend... then what??? He is only 17 years old.
What if he goes around fertilizing more gardens and has more accidental kids?
I personally... would NOT give your baby 'his' last name.
Also I would not use a 'hyphenated' last name. Hyphenated last names, are, legally taken as one whole name.... but if the name is NOT hyphenated... a person can legally, use either last name.
Just use your last name, for baby.
That is what my friend did, for her kids... when her boyfriend, was just a jerk. And still was.... even after the kids were born. And still is... even though her kids are now 16 years old.