This mountain bike touring trip below was in Feb. 1983, about 1000 KM from San Ignacio, near the center of Baja, to San Jose del Cabo, near the tip. There has been quite a change in the southern peninsula since that time. What was then a dirt road between Todos Santos and the tip, is now a major highway with buses every half hour. The 80 cent a night Hotel California in Todos Santos, where I stayed at, is now 80 dollars, no doubt partly resulting from fame from the rock song Hotel California. Before, no rooms had bathrooms and the common shower with cold water had a sign No Orinar. It is still a fine old building, with high ceilings and rock/adobe walls. Of course, the clientele no longer includes campesinos. Todos Santos itself is now a bit touristy, but there have been been improvements. Before, the downtown buildings were mostly shuttered and abandoned since the sugar plantations shut down decades ago. Now, the buildings are revitalized by shopkeepers selling coffee, pastry, books in English, trinkets and food.
Baja is on my future trip list.
Baja California is an ideal place for mountain bikes. Practically speaking, there is only one paved highway after you leave the border area. Most roads are single lane dirt used sporadically by ranchos.
On a previous trip to Baja I waited all day with my backpack to get a ride on a dirt road without any vehicle going in my direction. So this trip I brought my mountain bike. It is a Ritchey with a Blackburn rack. A gallon of water and my sleeping bag went on top of the rear rack.
My favorite spots were in crossing the mountain ranges at San Javier and at Narango near the tip. The latter single lane road is not on any map. I heard about it on a previous trip from villagers I stayed with. The granite rocks surprised me. The vegetation became quite lush. At San Javier (Xavier) there is probably the best preserved mission in Baja. The winding dirt road up to the plateau is quite spectacular, at first going thru a deep canyon, and later giving views of the Gulf and islands.
I encountered a group of three other mountain bikers on this trip. When I road on pavement I also traveled with some 10-speed tourers. We went to the best restaurants we encountered. Eating was one of the best parts of the trip. Although a typical Mexican meal could be had for under $1, we ordered courses like shrimp with garlic-butter sauce, or "pescado a la Veracruzano" (a spicy fish and vegetable stew). The cost? $2-$3 for a full meal. If you are in a village, ask the locals which family sells meals. They wouldn't have any sign since locally they are known.
Most of the time we went to a hotel in a town instead of camping since it cost only $1-$3. If you camp and are not in a group, the simple rule to follow is don't let anyone see where you camp. Water from ranchos and most small towns is safe to drink since it comes from wells.
One beautiful and interesting place we camped was on an island in Conception Bay (south of Santa Rosalia). During low tide the island becomes a peninsula. What amazed me was the fluorescent micro-organisms in the water. When you splash the water at night, you see what looks like yellow-green sparks. Sometimes you can pick one up.
The riding surface varies widely. Most places have hard packed dirt. But you can also expect small to medium rocky roads. Some places are sandy and one road I encountered was cobblestone! A few places have "washboard". This is where the springs of the ranch trucks form waves in the road. This tends to make you seasick or carsick (or bikesick?). I didn't encounter much of this but was warned by other mountain bikers that the road from San Felipe south toward Punta Prieta has five days of washboard with large rocks in some areas. This description was accompanied by various obscenities and an offer to see a saddle soar.
You probably will want to take the paved highway for part of the way. There is only one vehicle about every 10 minutes if you are away from a town. However, the Mexican buses don't stop for anything, so whenever there is an on-coming vehicle and a bus from behind, it's best to get off the road if you're moving slowly.
Now for some advice. The prevailing winds are from the north so go south. Take along a 16 oz. can of foaming chain lube or equivalent. You cannot buy any along the way. Check to make sure your panniers don't hit your cantilever brakes before you leave. Take any spare parts or tools you might need since there are no bike shops until you reach La Paz near the tip. I would include chain links and chain rivet tool, nuts & bolts, and a rear derailler if yours has ever gone into the wheel previously. Anything that's not inside a pannier will have a strong tendency to fall off. I took 3 long miniature bungy cords which I made up that worked quite well.