Do NOT take Greyhound, its Major pick up and drop off areas are not in safe areas of town for both LA and Las Vegas.
You have alot of other options such as flying through something like Southwest Airlines for as little as $50 one one way. Im sure their are others bus options as well that people will post, but Im not familiar with that area.Edited: 06 June 2018, 21:35
You should really consider flying between San Jose and Las Vegas. The flight is typically cheaper than the bus ride and only takes about 2 hours while the bus, with the transfer in LA, will probably take at least 14 hours. There are actually some nice bus options from the Bay Area to LA, including a new sleeping compartment bus that offers overnight travel (https://www.ridecabin.com/). From there, I'd probably take Megabus or Bolt Bus over Greyhound, but there's still the issue of the transfer time that's going to make this a time-consuming and overly arduous affair.
What are your reasons for considering Greyhound?
The typical choice is to fly between San Jose and Las Vegas, Southwest is the main airline on the route but there are a couple of others. That requires transportation from Gilroy to the San Jose Airport. But depending upon the date, airfare will be the same or lower than bus service. It also would be less travel time.
Greyhound's #6781 travels between Gilroy and Las Vegas with no change of bus. But it is an 11 hour journey. The route is via Fresno, Bakersfield and Barstow with a few 1 minute small town stops in between those cities.
There would be an onboard restroom on Greyhound but the only other service choices would be during the stops at the 3 cities I listed.
Of the two choices, I would suggest looking at flights from San Jose Airport first.Edited: 06 June 2018, 22:49