Hi Dawn,
Have you heard of Dream Cafe? It is over in Addison I believe. Their food is awesome and they have vegetarian and you can add meat to some of them if you prefer. I can't remember exactly where it is located but you can probably check yahoo yellow pages to find it. It had a very nice atmosphere and I do believe they have outdoor seating.
Cafe Express is pretty good too, although I am not sure what vegetarian dishes they have outside of their salads and black bean soup.
I just tried the new Masala Wok, a new Indian cafe here in Frisco today. It was VERY good and they had several dishes that were vegetarian.
My only other suggestion is the Cafe at Whole Foods or Central Market. There is a Whole Foods in Plano, Richardson and Dallas I believe. Central Market is off of Coit and George Bush.
Good luck!
H.