Conventions of all genres (fandom-based or otherwise) are usually held in one of two types of locations: hotels or convention centers. Just like with everything, exceptions exist (I have attended cons on college campuses and heard of others being held on state fairgrounds!), but you will generally encounter them in one of those two locales.
As with the content of Parts 1 (here) and 2 (here), the advice in these posts can be applied to any environment where there will be crowds, or when you are on vacation, or simply away from home for the day.
Let’s start with the more common of the pair: hotels. Most large hotel chains will have convention or conference space with a multitude of purposes, with cons only being one of them. This is a great source of income for hotels, since conferences, weddings, et cetera often come with people who will want the convenience of staying on site. This all accounts to something called attrition that can be a regular thorn in the side of someone renting the space…but that is a whole different topic for a whole different type of blog!
I honestly prefer hotel-based conventions, especially if I am staying in the hosting venue. If I have an attack, I can take a break in my room away from the hustle and bustle of the con (in the case of Omni, where I am usually working, I have a few people who can cover me for a short spell in the event that my attack gets so bad I have to lie down). If I am not staying in the venue, I can usually find a relatively calm corner out of the way to recover.
The Vendors Room at Omni [Fandom] Expo in 2015, taken early in the day on Saturday. Small cons are great if you prefer to avoid large crowds.