There are also crew positions, such as boom operator, that do not have quite as rigorous physical requirements as pilots. You can look up the requirements, or have your recruiter take your initial screening form to a flight surgeon and see if there are any glaring issues that are disqualifying or might require a waiver. This should always be the first step, and save you and everyone else in the process a lot of time.
We had a young guy meet a flying board, go through the whole process and paperwork, only to find at his flying physical that he had previously undergone lasik. At the time, this was not waiverable, and in addition to the time everyone spent working on his package, he was of course devastated. This could all have been prevented by running the person's history through the flight surgeon's office first.
So, even a doc in a MEPS (medical screening for all military applicants) likely would not know all of the physical exam requirements. So, whether ANG, Reserve, or AD this would be the best bet as a first place to start.
Finally, you can get something in wriitng, but if you don't meet the criteria for the physical exam, training, etc, the letter can be overturned by someone higher ranking to meet the needs of the military.