You should only go up 2in from factory rims. 18in rims should be ok but you pushing it kind of close, when you turn you dont want your front tires to touch your front finder.
they will fit, it wll raise you car a few extra inches, but it will work and look good, also here is a pic/video of a jetta with 18's http://c4.ac-images.myspacecdn.com/images01/75/l_27819d3ae1f3024742195fa339a49bef.gif
they will fit, it wll raise you car a few extra inches, but it will work and look good, also here is a pic/video of a jetta with 18's http://c4.ac-images.myspacecdn.com/images01/75/l_27819d3ae1f3024742195fa339a49bef.gif