Iconic sign, plenty of tourists, very few taxis.
On our last day, we decided to walk to the sign before heading over to the airport. Waking from Mandalay Bay to the sign took like 30 min in the hot sun, so I wouldn't recommend it. If you were to walk, do so at night. There's a police station in between, so it should be safe. Once there, though, don't assume there'd be a line of taxis waiting. We ended up being stranded there for another half hour (because walking back to the nearest hotel would've been even more painful). Finally one taxi pulled in to the parking lot and was able to take us to the airport, leaving behind other groups who were stranded like we were.
We saw other tourists taking a taxi here and having it wait for them. A decent choice, but also pretty expensive. Since if you want a picture from the front, you have to wait in line for like 15 min.
Best option might be by taking the bus, just be sure you have money to pay the fare!