Originally Posted by
relangford
Gee, if you LEGALLY cross either way, there are formalities both sides. If you ILLEGALLY cross from the US to Mexico (without tourist card, as needed), you can be arrested by the Mexican police.
Incorrect; there is no formality to enter MX from the US. You simply pass through a revolving gate. No contact with immigration/customs or any MX officials. No tourist card is required if you're staying in TJ or north of Ensenada.
When I traveled to TJ monthly for work (we have 3 plants in TJ), I had to purchase a day work visa ($ 20 if I remember..), which is the small building immediately to the right after your cross the border gate. Upon entering our plants, the security guard would keep my work visa in his possession while I was onsite, in case the police came by and asked to see the visas.