Las Vegas has a diverse system of public transportation for such a small city - most of which is focused on getting you from one hotel or casino to another - and despite the occasional traffic jam on the Strip, it's generally an easy place to get around. The city's major artery is Las Vegas Boulevard, which runs north-south through downtown and contains The Strip, a four-mile-long stretch that's the nexus of lodging, restaurants, and activities. The major hotels have shuttles that will run you, for free, to the tourist sights, but there's also a monorail which runs the length of the Strip and a tram/bus system for travel to the outer neighborhoods and the countryside.
It's unlikely that you'll want to bicycle around downtown Las Vegas, as the year-round heat and traffic make this less than comfortable, but for Outdoor Adventurers there are several outfits in the suburbs with road and mountain bikes for the trails in Summerlin and Red Rock Canyon, and hardcore cyclists who can handle the heat will find plenty of good roads for burning up some miles.
The Las Vegas Monorail runs up and down the Strip behind the major resorts with stops all along the route from the MGM Grand to Harrah's including the Convention Center and Sahara Avenue. It's the quickest way to travel this route, particularly on weekends when traffic is at a standstill. Tickets are $5 per ride or $12 for a one-day pass, with schedules running 7 am to 12 am on Mondays, 7 am to 2 am Tuesday through Thursday, and 7 am to 3 am on the weekends.
The Regional Transportation Commission, or RTC, maintains a fleet of public buses for tourists and residents that run both along the Strip and out into the Las Vegas Valley at large. A double-decker bus nicknamed The Deuce travels along Las Vegas Boulevard 24-hours a day with stops at almost all resorts. Tickets for The Deuce are $8 for a 24-hour pass, which includes access to all the RTC routes.
Taxis in Las Vegas are reliable, cheap, and safe, making them one of the best ways to get around the city. The initial fare is $3.30, with an additional $2.60 per mile, and those traveling in groups may find this the most convenient choice, as the split fare is cheaper than either the monorail or The Deuce. Rental cars are unnecessary if you're only planning to party on the Strip, but they are essential if you want to explore the outlying areas of the valley, and are easily obtained from rental agencies on the grounds of the hotels. All hotels offer free parking and free valet services, so if you're driving you'll always be able to find a parking spot.