If you want to go out into real desert from Las Vegas for the day then this is a fun trip out. If you aim to go as far as Rachel, Nevada and then back then it is a 151 mile drive from the centre of Vegas to Rachel. We had our own hire car and found it a very easy drive - easily done in c two and half hours.
It is important that you stop at one of the gas stations in Alamo to top up as there is nothing beyond there and it is wise to have a full tank.
You turn off onto Highway 375 at Crystal Springs. The sign is immediately at the junction if you want to stop and take pictures. Shortly afterwards you pass the Alien Research centre with its giant statue but we did not stop.
After you have gone over the first summit and between Mile markers 30 and 29 you get to Mail Box Road with the black mailbox (now white). We took our photos and were then entertained by someone driving up and emptying the said mailbox.
We moved onto Rachel and had lunch in the Little Ale'inn and then drove down the back road to the gate into Area 51. The people in the restaurant will give you directions. As long as you do not touch any part of the gate or the fence the guards will ignore you - just do not try to take their photograph as they do object to that.
On the way back to Vegas we stopped at the Pahranagat nature reserve which has a beautiful lake.