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.