On Kubuntu, it's under Settings | System Settings | Workspace Behavior | Screen Edges. Look for something similar in your settings.Is there any way to turn off the workspace preview thingy (technical terms FTW!) or move it to a different location in Mint btw?
Currently, if my mouse hits the top left corner of my screen, I'll get the option to switch to another workspace. I've lost count of the number of times I've done that as opposed to opening the gmail tab on my browser.