Here's why it's difficult to say definitively:
* Curve Variation: The scoring curve (how the raw multiple-choice score translates to a scaled score out of 5) changes from year to year depending on the difficulty of the exam. A 58.3% might be a good score one year and a mediocre score another.
* Weighted Score: The multiple-choice section is usually weighted differently than the free-response section. A strong performance on the free-response could compensate for a slightly lower multiple-choice score.
To get a better idea of how well you did, you need to:
* Consult the AP score distributions: These are often released after the exams are graded and show the percentage of students who achieved each score (1-5) for a particular year. See the College Board website.
* Consider your free-response performance: Your overall score depends on both multiple-choice and free-response sections.
In short, while 58.3% is a decent percentage, you can't determine if it's a "good" AP score without considering the other factors mentioned above.