If you want a fun, affordable, lively atmosphere I would try Cowgirl. Good margaritas, chips and guac. It is on Hudson right by W 10th. Mexicana Mama is a few doors up Hudson if you want more authentic Mexican.
Kick back with a Tiger beer at Fatty Crab, located on Husdon St. Really tasty and authentic Singaporean/Malaysian cuisine (pork buns, nasi lemak, asam laksa). Feel free to check out some pictures at: http://www.gobbl.com/blog/426