Some times its hard to catch the person that is in charge and sending a letter is not always that bad. Address it to the company name and someone will open it and if the company is looking for say lawn service they should direct the letter to the right person. Or addres it to the book keeper. If your looking for work it may be wise to go look at the site real quick and figure what you would charge for basic service and quote that price in your letter, if your quote is lower than the next guy, they may call even if they were not really looking to take bids this season.