Thanks for the help guys. Funny thing, today I went to my grandma's today and asked her and my grandpa about it. They were totally against it, they brought up a few arguments that I thought were intersting: if a soon-to-be mother uses marijuana the baby can be messed up, marijuana makes people go crazy, it damages brain cells, and they told me to tell my class that my granparents just don't like it.
**edit**
All of the above could have been applied to alcohol. So they weren't a whole lot of help, but everyone here has. I liked the link that was against the legalization for drugs, I didn't read it enough but from what I saw it did seem like most of it applied to the harder substances out there. After reading further down I found that I may have jumped to conclusions and I am thankful for whoever posted the link.
**/edit**
There were a few good arguments above, I especially like the one about second-hand smoke. Because that kind of a smoke is going to mess you up then your typical cigarette smoke.