Lisa, Welcome to All Things Plants!
There are a lot of variables involved in planning how much to grow of anything... first, as Tom said, how large your family is. And what you like to eat, how much canning/freezing you actually want to do, what grows well in your area, and so on.
I do disagree that you would need 36 tomato plants for a family of 4, though... I think half that amount would likely be more than plenty (again, however, depending on how well they do for you...)
Here are a couple of links with some guidelines:
http://www.gardeningknowhow.co...
http://www.almanac.com/vegetab...
Your county extension service may also have some info on what varieties do well there, how much to grow per person, and so on. Hope this is helpful!
