I met my ex girlfriends in random places, one at school, one at an anime convention (she didn't know she was bi til she met me and then we ended up dating for years!), one at a club but she was my "barsexual" friend, she only made out with girls at clubs, I met one in college and another in line at Burger King lol.
I am obvious though, I wear a lot of bi-pride stuff, so girls tend to approach ME.
My current girlfriend I met in high school
We can be found anywhere you just have to make people aware you're available, if you REALLY want to find them