I've gotten 1 or 2 customers using FB. Overall, it's been pretty much a waste of time though. It just doesnt strike me as the "go to place" to search for lawn care or any other business/service. When I want to find something I simply use google. It is the fastest and simplest way to find anything.
You will get much better results by creating a website and learning about SEO to get your site higher in the search engine rankings. You can also use Google Places for small business.
"Always do your best. What you plant now, you will harvest later."