I have done 3 or 4 grams in public, when I was younger. Everything went fine. I used to eat mushrooms very often, though. Nowadays if I am going to use mushrooms in public, I won't use more than 2.5g. Usually lower than that though, probably around 1.5 does fine for going out and being sociable.
Mushrooms in higher doses, make me more primal than other psychedelics do, and so I tend to do things that aren't considered normal really. I don't give a shit about normality when I'm on a good full dose of mushrooms. Normalcy can seem ridiculous on many psychedelics. For example, on acid I'll treat it as a game; it is fun to see how normal of a situation I can get myself into while being completely in acid world. With shrooms, though I am a maniac. I'd rather trip at a private beach, where I can take my clothes off and piss and shit wherever I please.
Despite being a maniac in high doses... btw I'm not too much of a maniac... I am at least nice, pleasant, and understanding. I just don't want to deal with shit. On acid and 2cs I think too much about rules. Rules don't phase me when I am on shrooms.
Then again, I probably keep my doses subtle enough that I don't flip out when I am doing acid or 2c's. THe only big doses I take are at festivals or in my home or a friends home....
.,,,, Bottomline. Eat mushrooms. They're awesome. Between 1 and 2 grams should be fine for going out. You may be quiet, but you'll probably feel pretty nice. Experiment dude. Start low. Eat 1 gram. Go out see how it feels. If you usually eat more than that, 1 gram may underwhelm you, but being out will make you feel nice. You'll be able to interact with your environment. And the situation will have more to do with your setting than the drug you took. I feel that it is the same as alcohol at this level. If you take 5 shots and leave to go to a show, you'll probably be pretty fucked up before getting there. But if you wait to get to the show and a have 2-3 drinks while there you'll be pleasantly buzzed. You can go and eat 3-5g of shrooms and be losing it in public. OR you can eat 1g and feel nice, slightly observant and interested in all things beside you. You ca be in a pleasant state....
Its tough to say man. Try it at home. Eat small amounts. Try it when there is nothing on the line. Eat 1 gram... when you can escape any situation if things get too powerful for you. IF you love mushrooms and are happy interacting in different situations while you are on them, you should be fine.
Blah, I'm drunk now... Ramble ramble ramble.