Can't speak for what the garden-variety reserve unit does, but I can tell you what current Marine Corps active duty policy is. You are fine to ride in your uniform, and you are required to be wearing some kind of riding jacket over it. You have to wear gloves, a helmet, and if not a full-face helmet, then wearing eye protection. Additionally, you need to be wearing either a road-guard vest or one of those Icon Mil-Spec reflective vests. If you are riding onto an actual military reservation, they will require you to produce proof that you have completed the MSF course (in the Marines, it's THEIR MSF course, not the civilian one). And of course, if riding on the reservation you also need to register your motorcycle with PMO IOT get a DOD sticker. All of the above is why I don't ride my bike on base... However, when I was in the reserves, I know nobody at my unit would have paid any attention to any of that at all, so, you may be okay. I got out of the reserves 5 years ago though, so that may be dated info... I think I'd go to drill first and find out what they want from you.
