Your body will let you know if it can tolerate a certain food. Large amounts of fat or sugar can cause dumping, but it only has to happen once for you to get religion!
During the first year post-op, you should be on a food plan designed by a nutritionist who consults with you through your surgeon's office. Following this plan will lead to the weight loss your surgery is designed to give you.
For the rest of your life, you can eat meals with others, but you'll figure out how big your portions should be and how fast you chew before you swallow.
No one in my life knows i had the surgery except my son and a few friends. And we eat together without any self-conscionsness because i control how much and what i choose. They see how little i eat compared to them, so no drama!