By what method? DWG? Something else? It would be cool if SU and Layout supported PDF layers.
Only exporting as a 3D file will export all the tags as layers, but when you import it from ilustrator youll have a lot of lines cause all the geometry is triangulated by some reason. If you want to create plans elevations an sections or a panel of your project, its better to use layout, i make all my projects exclusively with sketchup and layout, also when i was in the university I did most of my projects and thesis using layout.
Illustrator layers and SketchUp tags are two totally different things. Illustrator layers lie one on top of another like pages in a book. SketchUp tags are geometry in 3D spaces that are marked as being “together” primarily for the propose of changing view… there is not a simple way of forcing the two to align… LayOut on the other hand has layers just like like Illustrator. Maybe you need to be exporting from there instead.