Newcomer,
First I’d like to welcome you to the HSBBW. I’m not sure that it really matters. The larger colleges usually have a person that handles the administrative duties and probably screens all mail coming into the baseball office and distributes it accordingly. If you have spoken with someone prior to sending the letter, I would address it to that person specifically. At the smaller schools the head coach may be the only full time paid staff member associated with baseball. In that case I would address it to him personally. The protocol in this situation, if indeed there is a protocol, is not that defined.
I’m sure you will find the HSBBW helpful and hopefully you will stick around long enough that you will be “forced” to change your screen name.
Fungo