I agree with pretty much everything that was said. A couple of additional things that you may not be able to attend (trying to be thorough rather than depressing)
Normally the proposed ritual changes (and other things that clear the peanut gallery) come out of one conference committee and as such are likely to be one block of time and are broadly announced ahead of time.
Workshops. Out of 20 or more workshops, there are likely to be three or less that would be restricted to only brothers (or only members, however given that this occurs between semesters, unlikely to be many pledges there, given that most are likely to initiate in late fall). You are more likely to have problems due to *really* wanting to attend two workshops that occur at the same time than having nothing to go to due to everything scheduled at a given time being limited to brothers.
Initiation/chartering at Convention. At some of the recent conventions, I think some chapters have decided to have their brotherhood initiations at the Convention to give it extra specialness and I know of at least one chartering at a convention (Northern Arizona). Given the fact that there is a PG in New England right now, it is a possibility (probably remote though).
Leadership Seminars. The Leadership Seminars that are part of the LEADS program may have the requirement that brothers sign up ahead of time to take them. (I presume these are being done at Nationals) However you would probably simply be in the same boat as a brother who hadn't signed up...
You certainly wouldn't be the first Gamma Sigma Sigma sister to attend an APO convention
, your immediate past National President has been to at least one (though she is also an APO chapter advisor) as well as many others.
I'm personally glad that you want to attend, National conventions are a blast.