In april I paid 1400 pesos (~$125) for myself and my Kawasaki Concours, in cluding a shared cabin to go from Mazatlan to La Paz, actually Pichilingue sp? They even have a small disco on board, and sell Modelos for 20 pesos. passage was about 20 hours, and very smooth sailing. The ships name was the Puerto Vallarta, even though that's not where it went.
The road from Mazatlan to Durango is known as El Espinoza del Diablo, or the spine of the Devil. This road blows away any mountain highway in the US for sheer length of the twisty part. You just think it will never end. The switchbacks can be so tight that Semi's have to use both lanes to get around them, so watch for them, as well as errant goat herds. Twice on this stretch small bands of children, with a scarecrow looking thing on a stick tried to stop me, I presume to beg some money, although I didn't stop. Does anyone know the meaning of the scarecrow?