OK so the only way to find out what they like is to talk a little bit about it and see if they get bored, usually this means that they will stop talking or ask another question to change the topic instead of asking more questions about the mushrooms or whatever you're discussing. If they are into it they will ask relevant questions or comment like so tell me more about the death cap mushroom I don't want to get one of those by mistake. Its a two way street, they should be contributing too. Once you get to know people its a lot easier than starting a conversation though.

I just suggested edibles to give you an entry point that was accessible. I think you must have some pretty wild friends if all they think of is psilocybin you might want to have a default answer for that which will lead into something you do like ie No I'm not into that but I do want to grow the rare "blank" because I've never been able to find it growing in the wild. Mix things up by talking about getting outdoors to collect them, your photography skills ie did you take a class, I know you won't be spending all your time talking about spore prints etc but if you mix in other elements you give other people a chance to talk about their interests. Photography is really common, I love taking my camera to the botanic gardens on a day with sort of a dappled sunlight so I could jump in with that if you started talking about photography but not everyone knows everything so if you started talking about f-stops I'd be all um yeah I have a point and shoot I just like taking pictures so you need to keep it light. How do you feel about cell phone cameras, do you like instagram. Once you get to know what people are interested in you can go further into depth. (Usually they will smile when they are interested but like I said if they ask relevant questions you know they are)