I traveled the entire length of Baja this time last year....pulled my 40' fifth wheel with 3500 Dodge Diesel. Spent a total of 6 weeks there...3 down , 3 back.
You MUST have Mexican LIABILITY coverage issued by a MEXICAN insurance company. There are many both on line and/or at the border. COLLISION is not mandatory, BUT your American collision insurance policy generally does not cover Mexico. It used to be that a $50,000 liability coverage was enough, but the law changed in Mexico last year and you may want a higher limit....do your own research.
Crossed at Tecate border crossing...very quick, no traffic going in to speak of. Coming back out through Tecate was a bit longer, but much faster than other So. Cal crossings.
Diesel fuel available throughout trip with no major issues, but there is one long stretch. (I don't remember where exactly, but was in central Baja).
I would recommend carrying a five gallon can just in case. Ask for a SPECIFIC AMOUNT in pesos....most attendants are honest, BUT if you ask for a 'fill', or 'relleno con diesel, por favor'....they may not have zeroed the pump or cancelled it out before you had a chance to verify the amount...so only pay in pesos...ask for say '800 pesos' or whatever......they did not take ANY credit or debit cards throughout Baja for fuel. If you pay in dollars, the exchange rate will vary and never in YOUR favor.
My AT&T cell (with a Mexico calling package) worked almost everywhere...better than many rural places in USA.
There really is only one primary Baja road from USA to Cabo (paved that is)......with a few minor variations so everyone is on the same route..including trucks and local busses, other rv travelers etc. The road is two lane almost the entire length, with virtually NO SHOULDER and lots of washes, pot holes and 'topes' (speed bumps) . I traveled with another couple..I was in my 40' fifth wheel and they were in a 35' Class A with toad. We felt more secure traveling with another couple...none of us speak more than cursory Spanish.
The Baja road is also quite narrow compared to USA. The semis traveling this route can be relentless in hugging the center line...and a fellow rv'er we were traveling with had their motorhome drivers mirror taken off at 50 mph by an oncoming semi. It can be a bit unnerving. Also, we probably only averaged 40-45 mph or so the entire trip as we were always slowing for oncoming trucks, busses etc. just in case we were forced to the right edge of our lane.
We took our time, drove very DEFENSIVELY and enjoyed to journey. If you are driving something smaller and/or a motorcycle, there are non paved roads that head South...we just couldn't do those.
You also will encounter many military checkpoints throughout your travels.
The young soldiers (federales) manning these checkpoints don't speak English and are there to do a job looking for contraband, illegal immigrants from Central America, etc....if you aren't carrying anything improper, you should be fine, but it can be intimidating. Smile, don't say a whole lot, exit your vehicle when asked....accompany them if they enter your rv...only say what's necessary....they will usually open a few cabinet doors, look around and wave you on. If I remember, we had about 6 checkpoints on the way South, then about the same going back North.
Campgrounds are located at most cities along the route. Use the Church campground book for reference. Note that once you leave the main Baja highway, you generally are driving on gravel/sand roads. Some are in horrid shape, with pot holes, washouts and ruts plus low overhead wires and/or branches. Prices fell between almost free, to 20-30 dollars or so. We paid everything in Pesos. Available at local ATM's (not always working when you need them) or when you cross the border at any bank/kiosk. Do not just pull over and 'camp'.....not recommended.
Power at rv parks in generally higher voltage (think 130 or so)..and usually just 15 amp...some 20's/30's and I think I had one 50 amp in La Paz..but voltage was so high it kept kicking out my protector anyway. Water is recommended for non drinking..think shower/rinse only. Buy bottled water to drink. Sewer hook ups sometimes...but they can be broken/clogged or just not functional. You may want to use rv park showers/bathrooms etc whenever you can and minimize filling your holding tanks.
Don't expect USA type amenities/utilities and you'll not be disappointed. We had no major issues over 6 weeks, but it wasn't too hot or cold either. No reservations would be necessary. Go with the flow, arrive early in the afternoon in case you have to find alternate overnight. Do NOT travel after dark.
The people we met were wonderful, helpful, friendly and accommodating. We had a wonderful trip...use common sense, be a gracious visitor..there is so much to see and to do. Have a great time.