Mexico has different rules for Non USA citizens
I noticed to post suggesting you can get paperwork done in La Paz. USA citizens might be able to - kiwis can't.
Waiting to get paperwork sorted in La Paz is far too late for kiwis. And very time consuming and problematic in our recent experience.
Kiwis- and other non US citizens- have to get the paperwork done within 60km of the border crossing i.e. the bike paper work, and especially the 180 day tourist visa. You wont be allowed to buy a ticket for the Pichilingue ferry to Mazatlan without complete paperwork. We were threatened with having to fly back to Tijuana to get sorted. There was a phone number on a poster on the window at the Ferry ticket office that lead us to a solution but It was a hassle and it cost.