I got a pm from someone asking about passport requirements, and mentioning there is an "open border" in the area of Puerto Peñasco. There is no open border. Mexican authorities are lax in that area about requiring visitors to have passports and obtaining the Mexican tourist permit called a FMM. This is information below from a website about PP. I find nothing different. US citizens can enter Mexico at Lukeville without a passport as a result of the unique situation there with lack of enforcement by Mexican immigration authorities which is not official. On return however, people can be inconvenienced by having to wait and meet with US ICE personnel before being permitted to re-enter the US.
In order to travel to Rocky Point (Puerto Peñasco), you need a valid USA Passport or a USA Passport Card (or carnet) authorized by the US Department of State. This requirement has not changed since the US started requiring passports/passport cards to travel by LAND/SEA in 2009. Please know that you are not able to use a USA passport card when you travel by PLANE, you need a valid USA passport.
Children under 16 years of age arriving to USA from Mexico or Canada may present a birth certificate (original or copy). If child is traveling with only one parent or under the supervision of an adult, they must present a notarized parent permission document (authorization to travel).
If you are a resident of the USA of another country, we recommend you contact your immigration office before traveling outside of USA.