What would be your thoughts if you met a baby or child named Mary Jane?
I think it's a sweet name, and was very surprised to find that most of the responses on the name forum I frequent were that people would immediately think of marijuana or judge the family/parents for naming the child that.
Lots of given names are slang for drugs, and mary jane is a pretty dated/no-longer-used term. I'm familiar with it, but if I met someone called Mary Jane that's not the first thing I'd think of.