Chris Hartjes has shared his experiences in dealing with the combination of Postgres and CakePHP and convincing it to work with sequences in your tables.
I had been struggling with some weirdness that CakePHP has been displaying while trying to add some new features to the baseball league website, where Cake + PHP 4.4 + Postgres were deciding to just be sulky and not work together well.
Lucky for me, it turns out that the solution (for now) to the problem was to simply add the name of the sequence for that table as a variable to the model definition.
He includes the code for the Model that creates the connections between hos tables (belongsTo) and creates a sequence global to the class - note the naming convention.