Just received my dollars for my planned trip from the UK and noticed that the notes are all a new style from the last time I visited the US 3 years ago. The notes are different colours for each denomination and are a different design from the ones I brought back from Las Vegas. So can these old notes still be used or do I have to take them to a bank when we arrive in the US. Would a casino cage exchange them? Do they work in the machines? These notes would have been in general use in Aug 2009. Then again it might be just that they are new and the ones in my old wallet are well used.....???
All US paper money is generally green in appearance, but newer bills do have more colors to them (which indeed fade with use). The short answer is as long as you have bills from the past, oh.....20 years, all the bill readers should be able to handle them without problem. If they are a bit older, its possible some bill readers will not take them and you would have to exchange them at the cage. Bottom line: if they worked in 2009, they would still work today.
Of course, if they're really, really, old then this might happen: http://www.washingtonpost.com/national/tenn-police-apologize-to-man-arrested-for-suspected-fake-50-bill-that-turns-out-to-be-real/2012/05/01/gIQALEJ2tT_story.html
You will be fine. If the bills actually have some kind of problem with going in to a slot machine you can just take them to the casino cage and exchange them or push the "SERVICE" button on a slot machine and have a slot attendant change them.
I decided that I must be getting a little sad in my old age as I counted my daily budgets into seperate envelopes last evening as my wife looked on with that sort of smirky smile you ladies have at times...... The comment "you do know we are not going until March 2013"?? really was unnecessary. These things need careful planning and there really is nothing nicer than a wedge of brand new $100 bills in your hand.