Yes, any member can go. There are usually official delegates there from each collegiate and alumane chapter. They have a lot of work to do because there are various mandatory meetings. A lot of the business of the Fraternity is conducted during Convention as well as a lot of fun events... such as the aptly names "Fun Nite". I haven't been to Convention since 1997, so I don't know if it is still called that. Convention is also the time when they give out the awsome "silver" awards. I have gone both as a delegate and as a member at large. When I went as a delegate, I did not get very much sleep.
When I went as a member at large, I had such a blast! It is a little like state day in that there are break out sessions, time to meet a lot of Zetas and ZETA SHOPPING!!