@ Clevelandk1: That shouldn't be a problem. I've done that in the past, and I've seen it done many times. You want to ask permission of you're trying to get a shot of a specific subject (cosplay or whatever), but if you're just standing back and getting an overall shot, you should be fine.
I would encourage you to be at the Exhibit Hall on opening day and try to get a shot from the 2nd floor. Also, once inside the Exhibit Hall...you'll find plenty of things to snap pics of...just try to be mindful, as this thread suggests. Besides the Exhibit Hall, there are plenty of other photo ops...just look around.
What you DON'T want to do is be a creeper taking pictures of cosplaying ladies & gents without asking first. Judging by your post, it doesn't sound like that's your intent anyway, but wanted to mention this for other readers.