Let's see - the last hotel I stayed at was for a SF convention. Fee was $10/night/device. the last but one hotel I stayed at was for a professional conference; same fee. I don't travel much, but so far that's been my experience.
We selected the specific hotel we're staying at for this reunion independently, but they gave us the best price for rooms, so we all selected the same place. Their website says "in-room wifi" but doesn't specify free.
parenthetically, I tried to call them and ask about it, and got someone who didn't know what wifi was. I asked my mom to check for me, and she says they told her it was free, so i don't need to worry - right yet - about a portable wifi hotspot, but no research is ever wasted, and I may get one of these devices for the next time I'm going to stay in a hotel or have a problematic issue. For example, last time I flew, the airport had wifi, but also for a fee, and I had to sign up for a yearly service (which I could cancel as soon as I got home).