While the coast Guard does recruit for Food Service http://www.gocoastguard.com/Rates/FSrate.htm
I would suggest you go to a local communitty college and get a two year degree in cooking first, possibly while signing up for the Coast Guard Reserve in the mean time.
Do not be suckered into spending huge amounts of money or taking out big educational loans for one of the commercial cooking schools; very few of them are worth it. If you decide that is what you want, then make sure to choose a communitty college recognised by the state that grants an AA or AS degree, not just some certificate or graduation diploma that doesn't really mean anything.
I applaud you for wanting to straighten out your life. A lot of us have been there - done that. It is not a bad idea sometimes. I really liked my time in the Army.
I caution however that the policy of this homophobic administration is still DADT.
Best of Luck