Our son is an athletic recruit (non-football) and has a LOA dated early November. The Athletic Director does send notification to the MOCs that West Point has an interest in recruiting an athelete for a varsity sports team. As he was made aware of this during his official visit in September, it appears this is done very early in the process. The letter from the athletic department was also referred to in a letter from our Congressman that asked our son to complete their office's questionnaire.
A LOA is totally different and is from the admissions office when the candidates file is or nearly is complete (e.g., the LOA may contain contingencies such as the completion of the CFA or a nomination is received). Our son's high grades and SAT scores are such that he would be qualified to attend the Academy without the athletic interest. His letter actually states that a cadetship is being held for the candidate provided the contingencies, if any, are met and grades, behavior, etc., is maintained.
Now, I suggest you become in closer contact with the coach or recruiting coordinator for your team and arrange for an official visit, meet the team and coaches, get a feel for the campus and most of all, decide if you are ready for the commitment. This is a very big decision for you and it is most important that you make it with full knowledge of what will be expected of you and if this is the path you wish to take.