Passports are now required to re-enter the USA! Tourist Visas required at KM 21.
San Carlos is located just 320 miles due south of Tucson, Arizona. From Tucson you take Arizona State Highway #19 to Nogales. At the outskirts of Nogales take the Highway #189 bypass (Exit #4) (be sure to be on "Mariposa Road") which then becomes Mexico Highway #15 after you cross the border. San Carlos is about 4.5 hours south of this border crossing.
All roads on the way to San Carlos are 4 lane divided highways and are generally in very good shape. There are three "toll roads" you will encounter along the way with charges ranging from 20 pesos to 66 pesos.
There are daily flights to Hermosillo (HMO) from Phoenix Sky Harbor (PHX) on Aeromexico and American Airlines. Aeromar recently began 4 weekly flights from Tucson to Hermosillo as well. The airport in Hermosillo is located an hour and 15 minutes from San Carlos.
Since you’ll probably want to do some sightseeing while you’re in town (and taxis are relatively expensive) it makes sense to get a rental car during your stay. Each airport has both Budget (1-800-527-0700) and Hertz (1-800-654-3131) rental car agencies on location.
Tufesa has bus service to Guaymas, departing from Phoenix ($40), Tucson ($30) or Nogales, Sonora ($20). If you need to get a tourist card, be sure to tell the driver and they will stop at the 21 Km checkpoint. If you forget, this card can also be obtained at the Immigration office in Guaymas. Terminal locations and phone numbers are:
Phoenix: 1614 N. 27th Ave, 602-415-9900
Tucson: 5550 S 12th Ave # 148, 520-294-3780