It depends on what follows instructors.

Plural

Your parents met with your instructors.

Possessive Plural

Your instructors' expectations included that every student will succeed.

Yes, associate instructors are indeed considered faculty members.

In 2011 the DSA records 47000 Approved Driving Instructors.

This depends on the rest of the sentence

E.g. Your instructors are happy with your progress

or Your instructor's watch has gone missing, have you seen it?

or Your instructors' meeting was a waste of time as none of them brought their notes

Yes, riding instructors teach people how to take care of and how to ride horses.