Facebook Likes are important for 2 reasons. It means your personal/business name is showing up in the relevant searches and secondly you have something that a particular person or business is interested in.
Engagement with your target audience can be gauged but won't be accurate, again depending on the page type you have on Facebook and whether it is an open or closed group.
It is deemed crucial these days to have a "presence" on Facebook but shouldn't be your only method of contact. I am happy to discuss with any of my clients the best ways to generate business through PR and Marketing and my training and experience along with your vision of where you want to see your business will make an impact on where your business will be best channelled.