@BeachChick We love the Cosmopolitan and the rooms are very nice at the Cosmo unless you are above Marquee when the club is open as you will not sleep. My family and I love Jaleo and Raku.

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Jaleo
3708 Las Vegas Blvd S, Las Vegas, NV 89109

I just had date night at Jaleo (http://www.jaleo.com/index.php/contact/las_vegas) with my wife. Very good Spanish tapas and fun atmosphere. You then can head to Chandelier Bar (level 1.5 is the level I prefer) for drinks. I have not eaten at E which is a side room inside Jaleo but desire to try in the future.
Another very fun place with fantastic food is L' Atelier (http://www.mgmgrand.com/restaurants/atelier-joel-robuchon-french-restaurant.aspx). L' Atelier is arranged with seats around the open kitchen much like a sushi bar but with French food. The bread is fantastic at L' Atelier-yes the rest of the food is fantantistic. We eat at L' Atelier every 6-8 weeks as we are locals. If a dish you desire is on the tasting menu and your do not want to partake in the tasting menu you can ask if you can have that dish and they will try to accommodate your request. If you desire more formal experience dine at Joel Robuchon which is next door to L' Atelier.
Back at the Cosmopolitan Scarpetta (http://www.scottconant.com/restaurants/scarpetta/las-vegas) and DOCG (more informal than Scarpetta) are very good.
At the Aria we enjoyed dining at Sage (http://www.arialasvegas.com/dining/sage.aspx).
Off strip (you will need a car or take a cab) I would eat at Raku (http://www.raku-grill.com/) if you enjoy Japanese.

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Jaleo
3708 Las Vegas Blvd S, Las Vegas, NV 89109

As I read your post and the replies, I would tend to agree not to miss L'Atelier or Joel Robuchon next door. My wife and I dine at L' Atelier every 6-8 weeks as we have lived in Vegas 11+ years. I agree that Sage is wonderful as is Lotus of Siam. Another place I highly recommend is Raku but a party of 6 might be required to pre order or partake in an omakase menu (I would call ahead if this strikes you as a place to eat). Also, Raku is off the Strip. Additionally, I would recommend the $20 lunch at Estiatorio Milos at the Cosmopolitan (check availability on weekends). Likewise, I enjoy eating at Jaleo at the Cosmopolitan. I want to dine at E by Jose Andres (located within Jaleo) but have not had the opportunity.
If you are in the Cosmopolitan please have drinks at the Chandelier Bar; it is a great place to have drinks and people watch-AND you don't have to do bottle service to get a table.
Have a great trip.

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Lotus of Siam
953 E Sahara Ave Ste A5, Las Vegas, NV 89104

Jaleo
3708 Las Vegas Blvd S, Las Vegas, NV 89109

In N Out Burger is the choice.

If you enjoy Japanese food I would recommend Raku (http://www.raku-grill.com/). The restaurant is off the Strip and closes at 3am (closed on Sundays). If E is not to your liking Jaleo by Jose Andres (where E is located) might be an option for you. An option for lunch is the $20 lunch at Milos at the Cosmopolitan (but I am unsure if it is available on the weekend). Additionally, I would recommend L' Atelier at the MGM; I love the sushi bar seating but with small portions of French food.

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Jaleo
3708 Las Vegas Blvd S, Las Vegas, NV 89109