If you are heading to Las Vegas for the first time, or even if you know the place well, it's always a good idea to familiarize yourself with the Las Vegas Strip. My favorite map is from the Monorail and is a PDF file here
The Las Vegas Strip is almost always called "The Strip" in Las Vegas and refers to the stretch of Las Vegas Boulevard that is about 4 miles long. Mandalay Bay is the large resort at the south end of the strip, and the Stratosphere is at the North end. Note that the monorail route is from the MGM to the Sahara and you'll need to walk a fair distance to get to these two venues. Also note that the monorail does NOT follow the strip even though it serves strip destinations. The monorail rides from Hilton and Convention Center which are on Paradise, and then "behind" most of the Casinos. Always expect to walk a long way in Las Vegas unless you stay at the same casino, take Taxis, or spend your time downtown in the Fremont Street Experience area were the size of the casinos is much smaller and you can easily walk to several in a short time.