Clarity - you did well for your April trip. The round trip price you found from San Francisco of $685.00 is pretty typical.

I travel for a living and have posted most the "rules" you stated above several times. Its a crap shoot whether or not you'll get a better deal booking 3-4 months out or not....sometimes if planes aren't filling fares will drop significantly a month or even two weeks out.

When I book business travel I generally cannot until a month out. I also don't always have the flexibility to fly when I want. I use Kayak as a research tool but will also visit websites that don't do Kayak such as Southwest or Horizon.

When researching air be sure to look at the "hidden" fees - baggage, seat selection etc. Also take into mind taxes and airport fees - some sites don't list a "with tax" fare - Kayak does. They also have an option for you to calculate fares based on the number of bags you plan to check.

As far as Jamaica goes I'm out of touch only in that I fly on Frequent Flyer miles every year. My godson got about a $500.00 fare last year flying out of San Jose. It would be a stretch for me coming from Sonoma County but if you are actually "in" San Francisco or the East Bay you do have three airport options open to you. I've found Oakland is usually the most expensive and San Jose the cheapest.

When do you plan on flying? (season) That makes a difference too. Every airline knows every market's high season and prices accordingly. That and take into account holidays - even Presidents Day the fares shoot up.

Good luck - I'm sure you can find a fare lower than $685, give it time.