Majoring in biochemistry at school right now.
Going into Sophomore year.

Too late to start taking acting courses?
I'm really interested in becoming an actor.

No way

http://en.wikipedia.org/wiki/Dolph_Lundgren
"A graduate in chemistry from Washington State University, chemical engineering from the Royal Institute of Technology in Stockholm and the University of Sydney in Sydney, Australia in 1982"

Should I join my school's acting club? Facebook page but it's an open group with ~100 kids in it atm. Or should I try to get any local acting gig (even crew) just so I can get myself into the acting background?

I have no idea where to start. I live in DC btw.

I know very little about it but i think most serious actors start young. Usually they do some form of drama, theater, or performing arts classes and participate in clubs and performances relating to those things. I have no clue if its too late. I think so much depends on your talent as an actor. I think any expose and practice would be a step in the right direction.