I've always been open about my love of the franchise. Well, as open as an inverted person can be. It was booming in elementary school, so there wasn't any need to hide it. I remember having a Marill backpack and trading my snack money for Pokémon cards.
Yu-Gi-Oh! started getting popular in middle school and I got more into that, but I still played the Pokémon games and didn't really make any effort to hide it.
During my last couple years of high school, I got some of my friends into the Pokémon TCG, even though most people were playing Yu-Gi-Oh! or MTG. I sometimes wore Pokémon shirts (not that I had a lot, since it was rare to see them for sale around here) and I'm pretty sure I even strapped a Poké Ball to my belt-loop a few times.
I used Pokémon as the base of several of my assignments, like writing a short story "Lickitung Steps on its Tongue" in elementary and a newsletter about the arrival of Diamond & Pearl in high school (both were posted in the hallway and I got positive comments from other Pokémon fans). :)
I remained pretty open about my Pokémon fandom in college. I wore a Pokémon shirt on the first day, started up a small fan-club during my second semester, again based several of my assignments on Pokémon (like a Pikachu painting) and doodled them in my free time, traded with friends, and had lengthy discussions about how we could beat each others' favorite Pokémon (I don't think we ever did actually battle, though)... those were fun times.
I don't get out at all anymore, but my life still revolves heavily around Pokémon. 9 chances out of 10, I'm doing something Pokémon-related (be it playing the games, drawing them, reading about them, making up my own, or just thinking/talking about them in general). TPC, please hire me.
"If Pokémon were real" scenarios go through my mind far too often -- I have to remind myself that they're just cartoon characters and will never be real no matter how much I want to rub Wartortle's ears or poke Dunsparce's belly.