The speed limits in Mexico, on the way to Peñasco, are marked in kilometers. Please drive safely and at appropriate speeds. We wouldn't a bunch of Mexicans coming up here and driving at any speed they pleased, disregarding our laws. Be cautious when traveling outside the United States. Our liberties and relative freedoms do not apply in Mexico.
Traveling at night is less safe. The road is not as well marked with reflectors and reflective paint. Again, please control your speed. Also, they use another language on signage
Travel with safety equipment. Seems like a no-brainer, but when was the last time you used you car jack? Flashlights, water, first aid.
Please do visit Puerto Peñasco. You'll find the people to be kind. Be respectful and it will be returned. There are some horror stories, and those tend to circulate and have more of an impact.
Personally, I've made it to Peñasco for decades, had our wedding there a couple years back. The puerto has changed a great deal over the years, with all that an increase in tourists and residents brings with it. City traffic is worse, was never good. Be prepared to sit in a long car line at the border if you're returning on a Sunday.
If you're making your first trip I always recommend going with with a veteran Peñasco traveler. Learn the ropes, so-to-speak.
I say, go for it! Wear your sunscreen!