Depending on lane surface, generally I would say you do not want to be outside of 10 on Mexico City on synthetics (wood with a defined track area is a whole other story). 

For Mexico City, rule of 31 says the exit point at the end of the pattern should be 14.  In Mo Pinel's study, he says 10.  When I bowled on it, I played it very tightly trying to hit 15 at the arrows and 12 at the breakpoint or so.  I had the most success with a Zero Gravity.

One piece of advice, going into tournaments where I know the shot beforehand, I have found I have more success thinking in terms of the general area I am going to play, as opposed to specific boards.  Mexico City will play differently from house to house.  Once you start thinking about specific boards to play before getting to the tournament, it is hard to let that go.  I went into bowling Mexico City knowing I should probably be somewhere between the 10th and 14th board down lane and I think that helped me more than zeroing in on specific boards.

When I bowled on it (once), I had a lot of success once I actually used something that responded hard to friction. My Network @4000 gave me much more room than my Darkness @4000. I thought the Darkness would have been the ball to use, but it was too smooth.

I like strong core pearls on longer patterns.  The reason is that nothing will give you any out angle early, but the pearl sometimes give you a bit of hold if you don't over do it.  I also concur that you probably aren't going to be outside 10 board.  A lot depends on your style.  High rev and lots of axis rotation is going to be tough early no matter what you throw.