When can I take my newborn out in public? The pediatrician said to wait 2-3 months to be the very safest.

I agree. It is safest to wait at least 2-3 months, as your baby would have had some immunizations, but always avoid extremely crowded places or strangers kissing or talkin too close to the baby, specially during flu season.
Now. You do not need to wait. You and your child should get out of the house. Keep the baby away from anyone sick, and everyone should practice good hygiene. Dress the child appropriately for the weather, using yourself as a guide. All adults and teenagers need to have a pertussis booster.
Now. I disagree and when a newborn is absolutely properly clothed and not touched by people who are ill , should go out and have a normal time when the child born.