I've used Viana Lawn Care for a couple of years now and have always been grateful for their work, their prices, and their attitude.
First, unlike other lawn services, they understand that I have a dog with free access to the yard (via doggie door) and they remember to LOCK THE BACK YARD GATE when they leave! Other services were pretty careless about that -- and we don't want to lose a valuable family member because a yard crew doesn't care enough to remember the one and only instruction we give them: LOCK THE GATE! I trust Viana's guys.
Second, their prices were flat-out the best of all the lawn services who work on our block. I don't know how they can afford it now that gas prices have gone up so much.
Third, their work crew is always courteous and helpful and FAST. The work is done very efficiently and cheerfully, and I really appreciate it. The office lady is nice, too.
There are other good lawn services, but of the four that I have used, Viana is my favorite and I recommend them to everyone. (FYI, the number CitySearch gives is out of date; it's been changed to 703 250 2060 ).