Not big on pre-season predictions at any level. Football is so much about chemistry that the frequent pre-season formula of looking at returning starters, key positions, etc. and then making predictions is so often wrong. Even the coaches don't have a great sense of how all their pieces fit together and how to compensate for weaknesses and accent strengths until they see a game or two of live action. I am in violent agreement with Col. Henry that two of the most overlooked factors particularly in high school football (but apply to all levels) is line play and depth. Strong line play on both sides of the ball is one of the easiest elements to consistently apply week to week regardless of an opponents scheme. With regard to depth, injuries are inevitable and the ability to manage that while minimizing the drop off in quality of play is key to a successful season.
Having said all of that, there is one reasonably simple prediction to make about the PAL-Bay. Menlo-Atherton is simply at a different level than the rest of the league. Last year the combined score in their 5 league games was 167-18 with their closest game a 24-7 win over Half Moon Bay who went winless in league. MA has a combination of the biggest roster in terms of number of players and despite losing two of their top front seven players to University of Washington from last year will feature at least a dozen players over 220 lbs (I know not all big guys can play, but it really helps to have a lot of physical bodies at this level). They also feature two of the best skill players in the section in Anderson and Franklin (rated the #2 Junior in the state by most recruiting services). Their only question is at QB where they have the SHP transfer Price coming in and I am not sure if he has to sit out for the first 5-6 games or not. If so, they lost their returning starter Alexander to transfer, but do have Macleod who filled in admirably against Wilcox last year in the play-offs as a freshman. They do have a new coach and play one of the toughest pre-season stretches in the section playing three consecutive games against Serra, East (Utah) and Folsom all on the road. I will be surprised if they don't replicate their success in league like last year and if they aren't one of the top 3-4 teams in the section entering the play-offs.
The rest of the league should be fairly competitive with each other. These teams feature some nice skill players, well established coaching (outside of Terra Nova that also has a rookie coach), but almost all of these teams will have 30-40 players rosters with only 2-4 players over 220 lbs and will be challenged by depth and the ability to hold up with physical line play. Most of these teams will be forced to play a lot of their players both ways.
Per RMBR26 above - HMB is not in the Bay Division this year as they were demoted to the Ocean with Menlo School. The Bay league this year is Aragon, Burlingame, King's Academy, Menlo-Atherton, Sacred Heart Prep and Terra Nova.