Because of the many fraud attempts that occur in this city, getting cash is sometimes more difficult than in other places.
There are Automatic Teller Machines (ATM) located on all casino floors. Most accept bank/debit cards as well as major credit cards. Most also have a service charge in the range of $1 - $3 per transaction, in addition to any charges your bank may levy for use of an out-of-network machine. Therefore it is wise to try to withdraw as much cash as you need (and probably a little more) to avoid paying additional service fees.
Check cashing in Las Vegas is not quite so easy. Most hotels will allow their own guests to cash small amounts, but don't be surprised if a hotel will not cash your check. Even locals occasionally have trouble cashing checks.
By all means, avoid going to currency exchanges/check cashing services. They usually charge anywhere from a 5 to 10% (or more) service fee to cash an out-of-state check.