By turning on stats in user.cfg to show frame rate, I've found that turning on r_vsync in the same file has no effect. Perhaps this feature is simply broken and wasn't included as an in-game option for that reason. On the other hand, this issue might be dependent on ones hardware, so maybe someone else can confirm this.
Under the Settings location (user.cfg) section (and again under Vsync), two locations are mentioned for the user.cfg file. A lot of other sources suggest that both files need to be edited, but I've found that this isn't always true. The file in %LOCALAPPDATA% will usually change automatically to reflect the file in Steam's userdata folder when the game is launched. It seems that the only time this doesn't work for me is when I'm in offline mode, in which case I do need to edit both files. I'm not sure exactly what's going on here, but maybe someone can help figure it out.