I fish Cabo a good bit, depends on what type of marlin fishing you want to do. If it is stripies, late winter early spring . Blues start showing up in July. My favorite month is August for a couple of reasons, one I have caught blues, blacks and stripies then, sails, though seldom targeted, are there, monster dorado are there (my g/f caught an 65 lber August before last) tuna (schoolies) are reliable and wahoo can be targeted. But, best of all, august is off season and a 31 Bertram typically cost only 350usd. for a full day (I recommend the Mexi-time) and your lodging is cheaper then too. August is the hottest month there so bring appropriate clothes and sun screen. As for October, that is a good month, but the richest tournament in the world is being held then, you are going to pay premium for lodging and charters, if you can find a decent one, all the good ones are chartered for the Bisby black and blue. Good luck.