Good Paella near the Met
If you walk across the park afterwards to the west side, you could go to Cafe Ronda -- it's Argentinean-influenced tapas place, and while i've never had their paella and can't vouch for it, they do serve it...so i'd say keep it as a backup option if you should find yourself drifting west through the park after the museum and craving Spanish...
Otherwise, i'd recommend heading downtown...i like the paella at both La Nacional and Soccarat (sp?) very much...
239 W 14th St, New York, NY 10011
249 Columbus Ave, New York, NY 10023
259 W 19th St, New York, NY 10011
Toloache 82 is a short walk from the Met, on 82nd St, b/t Lex & 3rd. There is an excellent Veracruz-style paella ("Tumbada") on the menu.
Toloache 82 photos: http://www.flickr.com/photos/11863391@N03/sets/72157627846888083/
166 E 82nd St, New York, NY 10028
Don't know of any Spanish restaurant near the Met, but if you're willing to take a 15-20 minute cab ride, here are the nearest ones that I can think of:
La Fonda del Sol (in the MetLife Building in Grand Central Station area) has a pretty decent paella Valenciana, but need to order for 2 persons:
Solera (E53rd and 3rd): I've not had their paella, but I know that it's on their menu.
216 E 53rd St, New York, NY 10022
La Fonda del Sol
200 Park Avenue, New York, NY 10020