My current character wears Studded leather and has a dex of +5 which also happens to be his armours dex cap. does that mean my character can't fight defensively or rather, not gain the benefits from fighting defensively.
Fighting Defensively provides a Dodge bonus, which would provide additional +2 bonus to your AC. Not to mention, dodge bonuses are (I'm fairly certain) the only AC bonus that stacks with itself, so if you already have a dodge bonus working for you, this would add to it.