I would think it would. It is most likely a GSM unit which works on ATT. You might want to verify it operates on the same bands…

http://en.wikipedia.org/wiki/Nokia_5800_XpressMusic#Specifications

http://www.gsmworld.com/roaming/gsminfo/index.shtml

yeah I bought the same phone from Dubai, it works perfectly here in NY. Except the United States still doesn’t have the video chat compatibility yet. I used it for sprint and T-mobile, anything with a SIM card should work

If its the quad-band version, for sure it will….. if not, just check the frequencie that your 5800 works on, with the frequencies that are usen in the area you’re going to. You can check the phone operators here: http://en.wikipedia.org/wiki/List_of_United_States_mobile_phone_companies (they have to be GSM and be available in the area you’re going to.).

If you’re planning on buying a SIM in the USA, be sure to check you’re phone is unlocked.

And 3G might be a problem too, depending also on the frequencies used (and the tech used. The 5800 is UMTS/HSDPA I think).

Hope I was able to help ;D