Not that it matters, but interested to know if this is your first Mexico travel experience.
With that out of the way, we travel to Mulege/Bahia Concepcion most April/May's for reunion of my wife's side of the family. We cross at Tecate, take Hwy 3 to Valle de Guadalupe, spend a few days visiting the vineyards, then leave Miss Winnie with friends while we take our dinghy down Hwy 3 to Ensenada where we join family for the drive down Hwy 1 to Mulege.
Looks as though you are planning on taking Hwy 5 through San Felipe, Santa Rosalia, etc. I can't speak to parks or camping through there, but when you stop in Calixico for insurance (Sanborn's, Mex-Insur, etc.) they have turistico maps of RV parks. Or search on line. Except for the stretch from Mexicali to San Felipe, the rest of your route is more populated than Hwy1
We find fuel, gas and propane to be of good quality and usually cheaper than U.S. You will be thankful for your on board toilet.
You will have a couple of long, desolate stretches of road. Drive on the top 1/4 of your tank.
If you have a CB or walkie-talkies, check with your local Mexican consulate about their usage. They just can't seem to make up their minds.
Did I mention no guns?
Safety: I have been running the border since I was a child. In '72 I came back from my fourth tour in country and was invited by a friend to attend a quincienera in his hometown. Married the prettiest girl there and continue to run the border. But Mexico of '72 is not the Mexico of 2018. The border towns are crime ridden. As I write, the nueva generacion cartels are in open warfare in Tijuana and Mexicali. Keep your head on a swivel. Once you get south of Mexicali the crime level goes way down. Life becomes everything we go to Mexico to enjoy. We haven't traveled Hwy 5 for several years, but would have few concerns other than normal situational awareness. Same on Hwy 1. (Not so much on Hwy 15 thru Sinaloa and Culiacan)
We are pet free, but understand they are a problem to cross -- both ways.
You need a passport. They come in flavors these days. The familiar booklet, various specialized cards, etc.
At a minimum, buy Mexican liability insurance. Check with your U.S. carrier for their Mexico coverage (if any). You may want Mexican comprehensive.
Have fun! You are going to enjoy the place, you are going to enjoy the people, you are going to catch some delicious yellowtail. No matter what country you visit you'll find the good, the bad and the ugly. Our experience has been the good far outnumber the bad and ugly.
FYI: We have taken Miss Winnie to San Felipe once and never past Ensenada. We are just not comfortable with availability of DP repair facilities. Our insurance will cover towing back to U.S. from Ensenada. Our dinghy (Ranger or Camry) and your Navion are differently abled, as they say.
Fair Winds and Following Seas
Terry & Rosalina
2007 Winnebago Journey 34SE
Retired Navy Mustang & Navy Wife