Hi,
We did lacto-ovo vegetarian meals at each of the monorail resorts last summer. 1900 Park Fare was alright -- they had veggie maki rolls, but not much else. We didn't leave hungry, but it just OK. I do have to say the character interaction made up for any culinary shortcomings, however. Lady Tremaine and her daughters are a laugh-riot.
'Ohana was fantastic. We had veggie lo-mein, grilled tofu w/a few sauces, and white rice (plus the salad, bread, and dessert).
Chef Mickey's had a couple vegetarian entrees and a number of side dishes. We really enjoyed that as well.
Oh, Boma and Tusker House are fantastic for vegetarians.
Have a great time!
--Adam