How to Change My Son's Last Name

My question involves name change laws in the State of: Florida
When my son was born I choose his fathers last name to be on the birth certificate hoping the baby being born would wanna make him try to at least make him be in his sons life. He left me when I was 5 1/2 months pregnant. And is not at all in the babies life. He did not even sign the birth certificate. He now lives in another state and I have no contact with him what so ever. But my husband and 8 now want to change the babies name either to my madian name or my husbands. How can we go about that? (We have yet to file for the birth certificate)

If you're interested in pursuing stepparent adoption, you can change the name through that process.

Otherwise, as it appears that there's no order establishing paternity, and no custody or support order, you would petition for a name change as the child's parent with notice to the putative father (your son's father, whose legal paternity has not been established). Forms are available here. If he doesn't challenge the petition it will likely go through; if not you should expect to have to prove it's in the child's best interest to change his name.