I only showed my registration. They didn't ask for my title although I took a copy to be safe. Below is a good thread where you can learn a lot from. You'll need an FMM (Mex tourist card) and a Temporary Vehicle Import Permit (TVIP) except for Baja and certain areas closer to the border. It varies. www.advrider.com/f/threads/is-mexico-safe.546927/page-2625