I think anytime an APS summer or winter show is within driving distance, it is worth the trip! It is philately at its best. From the website, it looks like there will be 50-60+ dealers there. I always enjoy these shows whenever I can get to them.
To specifically answer your question, the meetings and presentations will vary. NEarly all of them will welcome anyone. A handful may be closed meetings for an organization, but that would be the rare exception, and it would be made known.
Most of the meetings are about about providing and exchanging information, and all are welcome. I would judge from the titles of the three you mentioned is that they are intended for anyone who might have an interest in this area.
You probably know about this, but here's the link to the show page:
http://stamps.org/AmeriStamp-Expo-ASEand they have a pdf of the tentative show schedule available for download.
To the left on that page, there's also a link to the dealers who'll be there. If you have some little missing holes in your collection and can never find those stamps, there's a dealer there that carries a very comprehensive inventory: A&D Stamps. It'll be one of the biggest booths there, probably up against a wall. Jim and Sue are very nice people, and you just tell them which countries and time period (or Scott #s) and they'll bring you a drawer. When you're through with that one, just tell them what you want to look at next. Sometimes there's a line of people waiting for them -- they're that popular. (I have no ties to them, btw, other than as a customer.)
I think you'll really enjoy the show.
Next year's show was supposed to be about half an hour from me, but they've just announced that they have to cancel it because renovations to the venue will not be completed in time, so it'll be here two years from now instead. Understandable, but disappointing. (They don't happen on the west coast all that often.)
-- Dave