Thursday Lunch, NYC Union Square and below...
 

Will be in NYC Thursday not surprised the places I would like to have lunch are booked - Grammercy, Del Posto, Little Owl. Looking for suggestions in the Union Square area, or close to ( Village, Soho, etc). Open to cuisine/price, but not too dressy.

Spice Market in Meatpacking, Fatty Crab in W. Village,
Cookshop in W. Chelsea on 10th Ave., Standard Grill under the Highline, W. Village/Meatpacking at W.12th and Washington..
Union Square..Danny Meyer's Union Square Cafe
These are all good choices..Little Owl is terrific so keep it in mind for the future.

Aldea is a great place. So is Gotham. Eleven Madison Park is outstanding. Craft Bar is fun. Casa Mono is good Italian. Inoteca is outstanding.

Aldea @ 31 West 17th St., New York, NY 212 - 675 - 7223.
http://aldearestaurant.com/
Gotham Bar and Grill @ 12 East 12th St., New York, NY 212 - 620 - 4020.
http://www.gothambarandgrill.com/
Eleven Madison Park @ 11 Madison Ave., New York, NY 212 - 889 - 0905.
http://www.elevenmadisonpark.com/
Casa Mono @ 125 East 17th St., New York, NY 212 - 253 - 2773. GOOD BAR DINING.
http://www.casamononyc.com/
Craft Bar @ 900 Broadway, New York, NY 212 - 461 - 4300.
http://www.craftrestaurant.com/craftbar.php
Inoteca @ 323 3rd Avenue, New York, NY 212 - 683 - 3035.
http://www.inotecanyc.com/

I love Eleven Madison Park and sometimes tables open up on short notice - but it's not casual.

A somewhat more casual option is Rosa Mexicana in Union Square - interesting, authentic Mexican.

i agree with casa mono, and union square cafe. they are both two of my top favorite's in new york. blue water grill is also very nice.

FYI, Gramercy Tavern has a large front room that does not take reservations and Little Owl has about 6 seats at the bar for "walk-ins", if you go for an early lunch, you should be able to eat at either place with no wait.