Are we allowed to have braces in the USMC?

You cannot have braces on in boot camp. If you want to get them after you are assigned to your unit, you must have written consent. Mainly because you can not have them while deployed.

Talk to a Recruiter. They can't actively recruit you until you become an upcoming Senior and are at least 17. That happens whenever the Seniors graduate next June. Your parents can't sign for you until you are 17. Parental Consent is required until you're 18. So you do the math vs. when the braces come off - usually 1-2 years, depending on your progress. You can't ship with them on, and regulations may have changed on whether you can join the DEP (delayed entry program) with them. A Recruiter can answer that. Good luck.

Call a recruiter. They should be able to answer this is a matter of seconds.