We went into these hotels telling them "I know you offer WiFi, but we are a tech conference, we're going to be using the WiFi harder than your normal event." They'd all say "It's fine", but they'd quickly learn it wasn't fine.
There wasn't really the option to use the cellular network for data at that time.
We eventually ended up running our own WiFi for quite a few years, because the venues consistently would just end up a smoking crater. The first year in Chicago the venue had this fancy centrally controlled wifi that was supposed to be all smart, but even after a field upgrade because the central CPU couldn't keep up, it was just a disaster.
Ended up going with a bunch of relatively inexpensive APs all set on low RF power, where the venues always wanted to have one or two APs on high power. Basically solved our problems.