"didn't Lee hope to gain support from the locals? Overall, did most Confederates view Maryland as "enemy territory"?"

Craig,
From what I have read in the past, you are correct. General Lee did feel that he would have support of the locals in Maryland. and as you state, many were sympathetic to the southern cause, but not all of them as Keith states. I read an article recently and I can't recall where at this moment that said that most Marylanders did want to help the confederates and went so far as to remove the handles from thier pumps to deny the Rebels water to drink. Wish I know where I read that.
He was a great general who did quite well in defending his home state, but he did not seem to do very well when he ventured out of it it seems to me.
Frank