There's a couple options depending on which state you are traveling from! - Fly into Tijuana and rent a car or hire a driver to take you to Valle - Fly into San Diego and take our shuttle bus to cross into Mexico (ETA to Valle: 2 hours, requires RSVP) - Fly into San Diego and rent a car (good for those who want to explore)
Your passport! Global entry does make the crossing faster, but it's not required.
We know it may be intimidating for first timers, but yes it's a safe and easy way to get to Mexico! You will see some not so glamorous areas while driving through the city, but that's pretty standard in any developing country.