I see everyone jumped into answer your question.. ROFL
We did a Hawaii cruise from the islands to Vancouver in the month of May a number of years ago. The seas were calm all the way (great luck as the ocean is unpredictable especially the Pacific).
The weather once leaving the islands got very cool, bring a good jacket and sweats in case.
Ensenada has a dock not like in the past where passengers had to be tendered on disembarkation.
As for the bus: can only tell you what I've read and talked with people who did the the ride to San Diego. Around 3 to 4 hours over not the best roads. Travels through a lot of poverty area but that is Mexico. As for time in Ensenada, doubtful. By the time you leave the ship, luggage, bus and the ride there will be no time.