I am a UK travel agent. I am planning a trip for someone who has not driven in the West before. They are driving late May, and I am recommending that they go from Vegas to Tonopah, overnight, then enter Yosemite via Benton and Lee Vining to stay in El Portal.

I had to do the "boring" route via Fresno, as is was Winter on my visit.

I am being too ambition suggesting "newbies" drive Vegas-Tonopah-Benton-Lee Vining (or will they love it!)

I think that route is best. They will need almost the whole day however to drive that boring road.!!!
End of May Tioga Pass in Yosemite (the most beautiful route however) is most likely still closed.

Sorry, I now see you want to have them drive through Lee Vining, which is Tioga Pass.
So be aware, big chance the pass is closed and they cannot drive that way.
They will have to drive then over Bakersfield and Fresno to El Portal. The next day they can visit Yosemite.!!!.

You just can't count on that route being open in late May. Here's a site with the historical opening dates.

http://www.nps.gov/yose/trip/tioga.htm#dates

And I agree with your assessment of the Fresno route being boring. It is.

You won't be able to tell them the route until a few weeks before the trip -- if then. Early this winter we haven't had a ton of snow and the snow pack isn't that deep. But if we get heavy - or even normal - snow from now through April, it is pretty unlikely Tioga Pass will be open in May.

But if the rest of the season is dry-ish then the pass might be open.

Where else are they going on their tour? Tahoe, San Francisco, or elsewhere?

I ask because if Tioga Pass is closed it is MUCH easier to get to Yosemite from the west.

For instance, if they are hitting San Francisco, consider having them fly from Las Vegas to SF, visit the city for a few days, then pick up a rental car and drive to Yosemite from there.

So what is the rest of their itinerary like? Then we can help you work out the best route.

On the offical Yosemite website you can see the previous opening dates of Tioga Pass. A lot will depend on the snows we get the rest of the year.

http://www.nps.gov/yose/trip/tioga.htm

If the pass is open, then your plan is very scenic!

Utahtea