Just got back from this itinerary and was in a balcony. The ship cruises about 10 to 15 miles off the coastline of Baja and land is only visible occasionally. It really doesn’t matter which side you are on as there is little viewing opportunity (other than just enjoying the ocean going by) and you should get just about the same exposure to the sun on either side of the ship, as it returns northward the exact same way as it cruises southward.
The best viewing opportunities are departure from your port (we sailed from San Diego, you definitely want to be on the starboard side) arrival into Cabo (port side for this) departure from Mazatlan (starboard side) and the departure from P.V. (Port Side).
Hope that helps.