Road to Cabo San Lucas
Well, there's really only one main road to southern Baja. Last November I took Mex Hwy 1 south from Tijuana/Ensenada along the Pacific. On the way back cut across to Bahia Gonzaga, North to Puertocitas/San Felipe. (That would be the only part I definitely would not recommend taking a trailer or a low clearance RV) The highways are a gamble depending on weather. Rain sometimes washes the roads out. A pickup can make it through, but maybe not a trailer. RV's could probably make it, albeit more slowly.
The further away from the border, the slower the pace and the nicer the people. We've got a timeshare in Cabo, and it was a very nice trip. Just recommend you bring along any spare parts you might need. Saw one or two Pemex without gas, but no problems with diesel. And although everyone suggested topping off at every opportunity, I went 500 miles easy on a tank. However I had 5 spare fuel cans with 35 gallons of #2 in the bed... There is usually at least one Pemex in each town of any reasonable size.
I also found the dirt roads to be a much more enjoyable than the highway, just because of the lack of trucks and buses.
Driving from La Paz to Cabo San Lucas at midnight was a real adventure. It took about 3 times longer because I went really slow. Really slow. There must have been a dozen cows, a couple horses, some pigs, and at least 100 burros in the road along the way. Toss in a couple Policia, some big rigs and an occasional drunk, and you can see why slow is good.
Make sure to get insurance. It cost me less to get an annual policy than for just 3 weeks. Go figure. Hope this helps, and do a search for Baja travel forums, there are some good ones.
TP