Passport and Border Info
Traveling to and returning from Mexico by land has fewer requirements than by air. Please read https://www.cbp.gov/travel/us-citizens/western-hemisphere-travel-initiative/faqs to answer all your questions
Do I need a passport/passport card?
Officially, YES. According to all government websites, all travelers 16 and over require passports (books or cards) at all land border crossings back into the United States. Homeland Security requires proof of identity AND citizenship to comply with the WHTI which is part of the Terrorism Prevention Act created by the 9/11 Commission.
Unofficially, many visitors say it's not a problem with a Driver's License and birth certificate to cross back into the US. At this time (Feb 2020), the Lukeville CBP has not been consistently enforcing the law. However that could change at any moment. Without a passport book/card, they can legally detain you while they "verify your citizenship". Citizens will not be denied entry to the US. But they can decide to delay you, which would be a bummer of an ending to a fun trip. Illegal immigration is a hot topic, and the border agents can be lenient one day and follow every rule to the letter the next. If you want to avoid the possibility of being detained coming back to the US for being "non-compliant", get your passport book/card.
Also (officially), Mexican border patrol is supposed to require you to show your passport and FMM going INTO Mexico. That's also not enforced at Sonoyta at this time.
Since a passport card costs $65 for 10 years, The cost of one margarita PER YEAR helps you get home smoothly. https://travel.state.gov/content/passports/en/passports/information/card.html
In addition, domestic air travel will phase in more stringent ID checks, and people who only use a standard driver's license will need to upgrade to a "Real ID" compliant one. Current regular Arizona driver's licenses are NOT "Real ID" compliant and will not be valid for domestic air travel starting in October 2020. Don't bother upgrading your DL--just get a Passport Card and you can visit Rocky Point whenever you want with no border issues AND you can board a plane for domestic air travel. (Please read more about AZ driver licenses and "Real ID")
What about children?
Children 15 and younger only need a birth certificate to cross between Mexico and the US by land. (From US Customs and Border Protection) Note: Both parents must appear with the child to get a passport card or book, or must fill out this form: https://eforms.state.gov/Forms/ds3053.pdf
"U.S. and Canadian citizen children under the age of 16 ... need only present a birth certificate or other proof of citizenship. The birth certificate can be original, photocopy, or certified copy."
Because of child trafficking and kidnapping, it is STRONGLY recommended to have a notarized "consent" form if both parents aren't present. (http://www.us-passport-service-guide.com/support-files/minor_travel_consent_form.pdf)
What is the READY lane?
The Ready lane machine will scan your RFID info so your citizenship is already established when you get to the CBP guard. *NOTES*-- Passport BOOKS cannot be used in the Ready lane as the chips in passports cannot be read from the required distance. All of the cards need to be held up against the driver side window (front or back) for the system to read. EVERYONE in the car 16 and older must have a card to use the Ready lane
Approved Ready Lane Documents
Do I need a tourist card?
Not at this time when crossing at the Lukeville border. Driving to Puerto Penasco "officially" requires a tourist card (FMM) since you're going beyond the border town of Sonoyta, however you will probably not be asked for it unless you plan to travel further into Sonora. At this time, only at some busy crossings in CA does Mexican Border Patrol require one. They're available online and need to be stamped at the border for validity. For visits of 7 or fewer days, there's no charge, Or you can get one valid for 6 months which can be used multiple times for 500 pesos (about $25 USD). (https://www.inm.gob.mx/fmme/publico/en/solicitud.html).
What is the "Hassle Free Zone"?
The hassle free zone has nothing to do with Passports or Tourist Cards. It applies to the areas where you don't need to get any special permits to drive your American-plated vehicle. Source and Source The free zone includes Rocky Point as well as further down the coast. You still NEED Mexican Car Insurance.