It is not too bad when you are going to a conference and have food intolerances. The two I have been to over the years, you are asked about dietary needs on the application form, so they can cater for you at the main meal times. For instance. At the recent SCBWI-BI conference I went to, the first main meal was on the Friday night at Pizza Express. They did have non-dairy options. I had dough balls to start with, chicken and pancetta salad for mains (which did have bits of cheese on - didn't know if it was dairy or goats) so didn't eat those, and for dessert I had a gorgeous raspberry sorbet, which I thought was made from real raspberries cos I tasted v raspberry.
The second day, at lunch time, I had tomato-based chicken curry with rice, and a few bits of tomato. This was v nice and quite healthy. The party in the evening was quite good, too. They had sandwiches, I had ham and branston, salad and chicken wings etc. OK for me, but my friend, Scarlet, who has gluten intolerance, it wasn't that good. I managed to eat a piece of the amazing cake and a couple of yummy biccies there. And I had no effects after that.
Sunday - At lunch time I had a moussaka with mushrooms and aubergine in, with rice. I didn't eat the mushrooms cos I don't like them. The aubergine to me tasted of nothing much. Overall it was good. But I had one niggle. I wanted to eat a bit of cake during coffee break in the morning, seeing at it was my birthday that day, but was told they all had milk in. Boo. Luckily I had my own free from biccies with me, which I ate, but I would've liked to have had something the others were able to have just for that day. I also had bananas with me and dried dates, which I ate during the weekend as snacks to keep me going.
Apart from the snacks at coffee breaks, I thought I was catered to quite well. I hope others, esp Scarlet, were too.