Completely depends on (1) how you're saucing it and (2) what else you're serving. Lightly dressed with butter/oil and herbs and Parmesan, with scant or no sides? I could knock back six to eight ounces, easy (not that I would necessarily let myself). Under a thick red "gravy" with chunks of vegetables and Italian sausage, served with ample sides? Three or four ounces, probably. And I are you making it fresh? I find homemade pasta is so much more delicate that it somehow seems less filling.
2 oz dried pasta is 1/2 cup cooked, which is an average serving, according to the Food Pyramid Guide, 8 - 1/2 cup servings per lb. But this in not what most people eat. I cook a 1/2 lb of spaghetti for the two in my house; that's a two-cup serving for each of us, (we're a little hungry) and I doubt whether you're only getting a 1/2 cup serving at your favorite restaurant.
It also depends on the shape of the pasta:
8 oz. uncooked small to medium pasta shapes = 4 cups cooked.
8 oz. uncooked long, thin pasta shapes = 1 1/2-inch diameter portion = 4 cups cooked.
8 oz. uncooked egg noodles = 2 1/2 cups cooked.
Two ounces of spaghetti = about 1 cup of cooked pasta, portion size the diameter of a quarter in your hand.
This is volume measure, btw.
So to answer your question, 2 oz dry pasta is the average serving for a single person.
Only you know how much you can eat.