Can you have legal guardianship on someone who is 20 in Georgia?
Unless you are declared incompetent and in need of a guardian... A 20 year old does NOT have a "legal guardian". You ceased to have a legal guardin the day you reached age of majority, which is 18 in Georgia. Living with someone does not make them ypur legal guardian. Only court documents that grant them guardianship make them your guardian. While some cruise lines have age restrictions, there are several others that will let you aboard.
What is "technically my guardian"? Either they are your legal guardian, or they are not.
first thing i'd try is to get one of your grandparents [with same family name] to sign and present that to the cruise people ... see if they don't ask too many stupid questions. if that doesn't work, I'd ask Family Court for a declaration that you are emancipated -- clerks will help you figure out how to do this
I don't think you are going unless you see an attorney to get legal paperwork.
They Pelted Us With Rocks And Garbage
If they're technically your guardian, they can sign for you. Thus the word technically.
You would have to have the court appoint a legal guardian.